Lace Java Fern -- brown leaves

[RiversGirl]

My Lace Java Fern is tied on driftwood. I am hoping it will dig its roots in soon. Recently however, its leaves are turning a dark brown. Does anyone know what might be causing this or what I could do? :help:

The light I have is a T5 and I make sure it gets between 6 and 8 hours of light daily.

http://i93.photobucket.com/albums/l70/RiverGarden/41214018_zps11049306.jpg (http://s93.photobucket.com/user/RiverGarden/media/41214018_zps11049306.jpg.html)

Thank you in advance for your thoughts.

[RiversGirl]

I was reminded to notate something here, in case it may have been a contributing factor. I was treating the tank with higher temperature. My heater maintained around 86°F for 6 days. This was done with a gradual, steady increase and then taken back down gradually as well. Could this have caused my Java’s leaves to turn brown?