well reduce light how ig is the tank if its small do a large water change. also if you have a cold water tank rasie the temp a tad . i had my bb dieing because i had cold water and it cuased greed water also very good mech filtration
I had this problem on a ten gallon when i set it up and it went away in like 2 weeks. I still keep the tank by the window and haven't had it come back. Do some water changes and just wait and see before you do anything else.