Killing my Phrag.

[Rhonda Svoboda]

I received this Phrag a month ago. I am killing it and I don't know why. Its leaves are so paper thin and delicate- two of them turned yellow, then dried up and died. I grow it with the same conditions as my Phap. (which isn't doing any better), I think its getting too much light but it dosen't receive any direct light. Its under grow lights, shaded by other plants.
I grow it on a heat mat to keep the plant warm in my Michigan home.
I water when dry. Does this plant grow in complete, dark shade? I don't know what to do.
Thanks