My mini phals keep loosing their roots to root rot

[lindasbabies]

I haven’t posted in awhile and I’m sorry for that but I’m having a problem with my two mini phals. They are potted in 3 inch plastic slotted pots, in bark from repotme.com. I’ve had one of them for a year, the other I got a few weeks ago and it has two flower spikes with beautiful blooms. I’ve been battling root rot with the first one ever since I got it. It will grow roots then they will rot then regrow them then they rot again. The second one I repotted as soon as I got it because it was in a moss plugg. I potted it in bark. It now has lost all it roots. What am I doing wrong?? This is so frustrating! My big phals are doing great. Thanks for any help you can give.

---------- Post added at 04:26 PM ---------- Previous post was at 04:22 PM ----------

I keep them in a southern window. The temp is 68-70 degrees Fahrenheit on any given day and humidity is around 47%.