Christmas cactus and Christmas tree leaf-like cactus sick?

Hi,
My Christmas cacti have recurrently been getting this mushy brown look at the base of the leaves. This one that I'm posting pics of already lost loads of leaves and looked like it was thriving with what's left for about 2 months. But now it's suddenly going brown at the base again!
I also have another one that started going the same, but I separated the different plants into 2 pots with new soil and they seem to be on the mend now.
The latest I've noticed is this other cacti with Christmas tree shaped leaves (sorry, I don't know the name) that's also started having what looks like the same problem.
Any tips on what I can do? Could it be some kind of disease that's spreading among my plants?
Thanks!

#1 looks like the worst case of scale ever. Spray it with insecticidal soap or another insecticide that says it treats scale. You will have to do this once a week until the scale doesn't come back. Yes, it will spread to your other plants. Quarantine.

#2 looks like too much water. The soil should be damp but not soggy. If the soil holds too much water, the plant will rot from the roots up. Did you notice if the plant got a little wilted looking before the leaves started rotting?

If you re-potted and the plant is looking better, you may have solved the problem. This group of succulents are epiphytes. That means they are not naturally rooted in soil but live in tree tops rotted in the decaying plant matter. So, the needs are bright indirect light, go VERY lightly on the fertilizer (if you fertilize at all) and damp, not wet, fast draining soil.

Daisy

PS: #1 is a Zig Zag Cactus (Cryptocereus anthonyanus) and #2 is a Holiday cactus (Schlumbergera sp) with a palm tree coming up in the middle of it.

Hi Daisy,
Thanks for your help!
For #1 OK, I'll get the insecticide and spray it.
For #2 the Holiday Cactus- yes, they definitely wilt and go all weak before they start rotting. The ones I re-potted I just put in regular universal soil, so I guess that helped. For this one, I'm thinking I have a bag of orchid potting mix- do you think it would be a good idea to mix some of this with the soil or even pot it in this only? This would definitely ensure good drainage. I have fertilized a few times because I've fertilized my orchids (no flowers on them), so I definitely won't be doing that again.
Thanks!
E.

Oh, and it's funny that that palm tree is coming up in the middle... I had a feeling it was something I shouldn't pull out and it was also looking like that to me but I haven't had a palm tree close to it as far as I know... so it's a mystery how it got there!

If they are starting to look good, I wouldn't re-pot again. Just don't water until you can't feel moisture an inch or more down into the soil.

I'm glad I could help.

Daisy

Just to be sure, this holiday cactus that's starting to rot again: should I just hold off the watering for it to dry out and do you think that will stop the rot from spreading? Or would it be safer to repot it just like the others?
Thanks!

If the roots are rotted, there is no saving the plant as it is. The roots rot and then the bottom leaves and so forth until the rot consumes the entire plant. The best you can do now is take cuttings from the top of the plant and start over. Cut at joints above the rotted leaves. Leave them to dry for a day or so and then lay the cuttings on the soil with the leaf joints in contact with the soil (push them down a little with your finger). The cuttings will root at the joints. Water once and leave them alone until the soil is dry again. Hopefully, some will root.

Daisy