Phal leaves yellowing?

[butterfly_muse]

Morning, everyone.

I have a phal that is yellowing its leaves and I can't figure out why. The very bottom one yellowed and came off, which is normal, so I didn't think anything of it.

But now the second one up is yellowing in the middle. The roots are strong and there are many of them. I repotted a few days ago into a sphag/bark mix, as solely bark was drying out way too fast with the a/c running and the hot days that have crept up on us.

The phal is in front of a west facing window, which has its blinds down all day. There is an a/c vent next to the book case it's sitting on but it's not near the edge, it's on the other side of the book case from it...still, the air is cool (generally around 70-75 by the a/c vent) and circulates, so I'm not sure what's wrong.

I water about once a week and fertilize every 2. What am I doing wrong? Is it getting too much sun? They used to be in a shaded south window at our old place and were happy. Ever since we moved they have been not happy. Should I maybe move them away from the window? As an experiment, I moved one of my phals to a bookshelf about 3-4 feet away from the window hoping maybe that would help. I am really lost as to what to do.