Yellowing leaves

I have 2 passion flowers and 1 hoya that have leaves that are turning yellow. The veins are still green. It looks like they might have a magnisium/iron deficency but none of my other plants have this issue. They are in small pots but I have very limited experience with these type of plants. I'm using our well water which is alkaline.

If your water is alkaline, then your soil probably is too and when your soil is alkaline the plants can't take up things like iron and magnesium.

That's what I thought too. They're in potting soil but like I said I do water them with well water. I water almost all my plants with well water do these types of plants just not tolerate it well?

Some plants definitely handle alkaline conditions better than others. I checked Plant Files, and both of these can handle slightly acidic to neutral or maybe slightly alkaline soil pH, but they may not be happy if your pH gets too alkaline. That being said, I have several different types of passion flowers planted in my garden in alkaline soil and they're doing fine. I don't know how often you fertilize, but if you're not doing that on a regular basis you might try giving them a balanced fertilizer that contains micronutrients and see if that helps. But if you've been fertilizing regularly then I'd try to fix your pH and see if you can water with bottled water, rain water, etc. Or you could try adding a little bit of vinegar to your well water to lower its pH...if you do this I would buy some pH strips first like you would use for pools/hot tubs and check the pH before you water your plants with it to make sure you didn't drop the pH too low.

Thank you for your input. I fertilize them regularly so I guess these will be on the list to get onlty distilled water. Right now they are getting a gentle rain which we really need here. By the way, where is Dublin? I'm originally from the San Fernando Valley.

The other thing you might try is switching to a fertilizer for acid loving plants--I think sometimes those have ingredients in them to help keep the pH lower. Depending on how alkaline your water is it may not be enough to fix the problem though.

Dublin in the SF Bay area--a bit inland on the east side of the bay.

Ok I must be doing something right because new leaves are coming on that look good.