I noticed one of my corys sitting motionless on bottom of my 55 gallon planted community tank in same place almost thought it was dead then later it moved and sat on top of this plant again rarely moving at all. Very thin tail and not eating. It has this whiteish patch on it. All my other fish neon tetras, green neon tetras, flame tetras, green neon rasboras, zebra danios and blue dream shrimp seem fine for now. I know I need to clean bottom and do water change as it's been couple weeks since last. Just hoping to be able to treat and save this fish.
PH 7.3
AMMONIA 0.5 PPM
NITRITE 0 PPM
NITRATE 5 PPM
KH 3
GH 12
Temp 77°F