I have a few tiger barbs who have been flashing and scraping for a few weeks now. There are no signs of parasitic infection, no ich spots or velvet, no fast gill movements, they're eating just fine, water paramaters are perfect (ammonia 0, nitrites 0, nitrates 10ish). Just to be safe I started treating with Coppersafe last week, but there seems to be no improvement. What else could be causing this?