Taiwan moss turning yellow?

I have Taiwan moss that has been pretty happy in a terrarium for quite some time. It’s a high humidity terrarium with an open back that has a large water reservoir and a fog maker that goes off every other hour to ensure the humidity doesn’t drop too low.

I also have a pretty bright light on a timer that gives the moss light around 8 hrs/day. At first the moss loved this and flourished and was a lush green, but lately everything is starting to yellow a bit. I can’t tell if the issue is too much light, a water issue, humidity, or perhaps growing the moss on a nutrient deficient surface?

https://imgur.com/a/kgOc78x

by NoiziCat