phaleanopsis leaves/stalks turning red, flowers wilting

[lily]

one of my phalaenopsis plants is turning red. the leaves are becoming tinged with deep red, and one of the two stalks has turned completely red and the blooms on that stalk are now wilting and falling off. the other stalk is still dark green and the blooms are still healthy looking

it is planted in a mixture of bark chips/charcoal/perlite and has been watered once a week since i got it. the mix always dries out completely before watering. there are no signs of root rot (abundant, healthy looking green roots). it has lost two bottom leaves, but has two large leaves that seem healthy other than the strange red coloring around the edges and on the bottom side of the leaf.

it has been living in a bathroom that receives a moderate amount of low light throughout the day - never any direct sunlight. i'm wondering if maybe it is not getting enough light?

any ideas as to what could be causing this? i would like to address whatever problem it has right away!

thanks in advance!