This was one of my signs when I had my bacteria problem which was brought on by stress. I think if you can find out the reason for the stress and solve that then plenty of waterchanges and complete dark for awhile until feeding gets back up to full and slowly start uncovering part of your tank for awhile you will be able to avoid meds. It doesn't look that serious yet so this should solve it.
As for the stress. I'll ask the usual questions to you:
Size of tank?
water parameters? (ammonia, nitrite, nitrate)
how often and how much water do you change out?
Are you using tap or r/o and what type of water conditioner?
temp of tank?
What are you using for filtration? (powerheads, filters...ect)
What are you using for airation?
How long has your tank been up and running?[/quote]
and you can never go wrong answering these...
shut the lights out for a few days? just a thought cover the tank maybe...