hardcorals tissue loss
 

what causes the loss. notice my acro loosin tissue as well as another.

thats not much light for acro

oh?? so update lights?

Shouldn't cause Tissue Loss though.
Is the tissue flaking off in chunks?

It could be a number of things. Not enough flow to flush away debris, chemical warfare in the tank, physical warefare and encroachment of other corals, etc etc.

Do a water change, run some carbon and hope for the best. That's all I can really tell you.

It isn't because of light. Lack of light willl make them fade over time, but not lose tissue. How quickly are they losing tissue? Could be RTN, could be acro eating flatworms, could be water quality, etc

Usually RTN happens quite quickly, so keep an eye on any more tissue loss. Some people have said that they've walked away for an hour and come back to a totally bleached acro. :( Hopefully in a day or two you'll see faint colour growing back on the exposed areas. This would be new tissue. I'd then seriously look for a nudi or flatworm.

It's hard to give an answer to this question because it could be anything...

I agree with Brad those lights are sufficient for acropora. Don't worry about that.