So I've been keeping six orchids for about 6 months now, and I've noticed two of them have been tilting more than they were before. I removed and cut off unhealthy roots a while ago so I expected them to thrive but I'm not sure what's going on now.

One of them still has a healthy stem and leaves with some nodes growing, although the other has half of its stem turned into this chalky-like texture that just looks dead.

I don't know what's going on. Should I change their substrate?

I also find that even when I water these orchids only once a week they still stay damp/moist for well over a week so I don't know if I overwatered them and caused some sort of root rot that way. And since these orchids stay damp for so long is that a sign that something is wrong or needs to be changed?