Yellowing Leaves on a Phal

[QueenofSix]

Hi all,
I just stumbled on this forum this morning, after searching for help with my phal.
I bought it two months ago from a reputable garden centre. I seem to kill all of my plants, so I'm sure that the current issues are completely my fault.
The orchid flowered beautifully and dropped the last of its blooms last week. I cut the spike last week, and noticed that two of its leaves are turning yellow and have gone soft and wrinkly.
I did some internet research and realised that I'd let the phal get too dry and I hadn't fertilized in a while. Per the advice I found I watered the phal and added a small amount of fertilizer. I also removed the phal from the room it usually lives in, which is south facing and has lots of indirect light to a room that's a little darker.
The two yellowing leaves are getting worse though the rest of the leaves still seem healthy.

Any help anyone can offer would be so appreciated. I love orchids but I have a black thumb, I guess.

Thanks!