Since Wednesday I've noticed around 5 of my cichlids scratching off the sand and intake filter. Water test done and Ammonia 0, nitrite 0, PH 7.8 and nitrate 20. No signs of whitespot but some cichlids do have stringy white poop. Unsure what to treat them for? Any suggestion? Could this possibly be gill fluke or even/also signs of Malawi bloat?