Root rot in peace lily - Can it be saved?

In spring, I moved my peace lily to a slightly less bright area and started spraying with mist because I read online that peace lilies like humidity. It ended up harbouring powdery mildew, but that went away after I washed/wiped it off and stopped spraying completely.

It's been a long time since then and now I noticed the following:
-New leaves growing yellow
-Powder on surface of soil, and only some of roots at base of pots covered with powder and starting to go brown at tips
-No wilting and all the old leaves are still green?
And I'm sure my soil was free-draining, but I noticed that in most my plants water doesn't run out of the holes properly until I tip it slightly sideways.

Is there any point in repotting as soon as possible?
Also, I have always considered repotting my plants when roots start growing out of the bottom of the pot, but I've always been held back by the fact that the best time to repot is in spring or when new growth has started. Should I just repot whenever the pot is outgrown?

Thank you.

I wonder if something else is going on.

A plant with root rot or too-wet soil will almost always wilt. As the water excludes oxygen from the soil the roots have a hard time surviving, but anaerobic organisms thrive, eventually the roots die.

Powder at the soil surface might be any of several things:
Salts from water or fertilizer. This would also make leaf tips turn brown.
Fungus. There are some that look like powder.

Here is what I would do:
Add 1 tablespoon (15ml) of 3% Hydrogen Peroxide to a gallon (4 liters) of water.
Plunge the whole pot into this and hold it down until the bubbling stops. Then lift it out and allow it to drain, tipping it sideways is optional. Let it go somewhat dry before watering again. Not too dry, Peace Lily (Spathiphyllum) prefers being fairly moist, as long as there is also room for air in the soil.
The hydrogen peroxide will add a bit of oxygen to the root zone and this should discourage any anaerobic organisms. This low dose is OK for the plant.

Other option: Repot it into soil that has fairly large pieces, not fine particles. The coarse pieces can be something like bark sold for orchids. This will hold water, and the gaps in between will hold air.

I would follow Diana@s advice by re-potting the plant into FRESH more open soil to allow better drainage, I would even change the pot, as the one your using is not draining excess soil quickly enough,
I would imagine also that right at the beginning when you moved the plant to a more shaded area, this prevented the soil from gaining the warmth it was getting hwen in it's original possition therefore the soil became much cooler and the water was NOT allowing the roots to dry out naturally.

These plants need good light BUT, NOT direct sunlight, to give that type of good light you should have is good bright sunlight BUT give the plant shade, I would give the shade by either placing the potted plant under an umbrella, or where some object causes shade at the pot,
Only water after you test the soil for dryness, I think sticking your finger into the soil, if it's dry, cive water from the BOTTOM, that is place the pot unto a shallow bowl of water and when the TOP of the soil feels wet, you lift the pot out the bowl, lay aside to drip dry. place it back into the brightness under a shaded bit.

I never mist these plants until the foliage looks soft or a slight wilting, SOOO when you say MISTING, all you do is use one hand to lift the leaves upwards as you mist the underside BUT, dont absolutely soak the plant.
Lastly when you re-pot into nice new fresh soil, make sure you DONT use a pot too large, these plants will only flower when the plant roots have more or less filled the pot, IF by then you have to re-pot again you only use another pot maybe 2 sizes upwards and then wait till that larger pot is filled with roots again, I always give a feed around spring time by using a seaweed liquid feed added to the watering bowl for the soil to soak it up, only do a liquid feed half strength for the first couple of feeds at the start of the growing season, Around March/ April; and stop this feeding around August to allow the plant to go into winter resting period always read the dosage on the feed bottle as over feeding is just as bad as NO feeding.

Hope all this gives you some hope and confidence to save your plant BUT if the plant does die, then you will be well prepared for next time you grow these plants.

Best of luck, and enjoy your new found gardening hobby.
Kindest regards.
WeeNel.

I would follow Diana@s advice by re-potting the plant into FRESH more open soil to allow better drainage, I would even change the pot, as the one your using is not draining excess soil quickly enough,
I would imagine also that right at the beginning when you moved the plant to a more shaded area, this prevented the soil from gaining the warmth it was getting hwen in it's original possition therefore the soil became much cooler and the water was NOT allowing the roots to dry out naturally.

These plants need good light BUT, NOT direct sunlight, to give that type of good light you should have is good bright sunlight BUT give the plant shade, I would give the shade by either placing the potted plant under an umbrella, or where some object causes shade at the pot,
Only water after you test the soil for dryness, I think sticking your finger into the soil, if it's dry, cive water from the BOTTOM, that is place the pot unto a shallow bowl of water and when the TOP of the soil feels wet, you lift the pot out the bowl, lay aside to drip dry. place it back into the brightness under a shaded bit.

I never mist these plants until the foliage looks soft or a slight wilting, SOOO when you say MISTING, all you do is use one hand to lift the leaves upwards as you mist the underside BUT, dont absolutely soak the plant.
Lastly when you re-pot into nice new fresh soil, make sure you DONT use a pot too large, these plants will only flower when the plant roots have more or less filled the pot, IF by then you have to re-pot again you only use another pot maybe 2 sizes upwards and then wait till that larger pot is filled with roots again, I always give a feed around spring time by using a seaweed liquid feed added to the watering bowl for the soil to soak it up, only do a liquid feed half strength for the first couple of feeds at the start of the growing season, Around March/ April; and stop this feeding around August to allow the plant to go into winter resting period always read the dosage on the feed bottle as over feeding is just as bad as NO feeding.

Hope all this gives you some hope and confidence to save your plant BUT if the plant does die, then you will be well prepared for next time you grow these plants.

Best of luck, and enjoy your new found gardening hobby.
Kindest regards.
WeeNel.