Mold and root rot after moving to S/H

[wciu]

I recently acquired a Phal Equestris, the medium it was in was pretty broken down so I thought I would try S/H with it. It has one new root coming out, so it should be fine o repot. The air roots were mostly fine, but roots in the old medium were all rotting. So I can cleaned them up, and repotted under S/H, with a ziploc bag over it.

After a few days, I noticed that a number of the roots are turning brown or black, some are shriveling up, and I can see some white mold on some roots as well. The new root spike is also dying off.

Is this normal? Should I clean up everything and try to repot again?