Why are the phalaenopsis roots turning purple?

[Orchid grower]

Hi everyone, Ive had a phalaenopsis noid for a few years now. It's always been healthy but I repotted it recently and I started to notice some of the roots starting looking sick - they started turning paler or red/purple and looking dried out or mushy. I took it out of the pot and was surprised to see how purple some of them have turned. My guess is that the media I potted it in was finer and it's staying wetter longer than usual.

Please let me know if you have any idea what could be going on. I really love this noid.

Thanks!