Maxerillia Tenuifolia with Yellow Leaves

[Bethy]

I am so happy, my Max. Tenuifilia is flowering. But I don't know why some of the leaves are yellow.

The yellow leaves do not have a flower - so I'm guessing they are older.

Also, my winter temperatures are pretty chilly - down in the mid-50s and highs in the mid-60s F. I was worried it was getting too cold, so I placed it in a seed mat.

Any ideas on what causes Max. Tenuifolia leaves to turn yellow?