Fry acting weird. Looking for suggestions

[Snakeeyes]

'm looking for some advice from fellow breeders. I've got this batch of fry that are about 6 weeks old and quite a few of them are showing very odd behaviour. They will suddenly turn dark and stop moving and start to turn almost vertical and shake there heads then after a short period they snap out of it, kinda like they had a seizure or something. But if I tap the glass or try to catch them when it happens they instantly take off. I treated with parazipro last week for 7 days strait to eliminate any chance of flukes even tho no other fish in the system show the same behaviour but I still suspect it could be flukes and I have no access to formalin or potassium permanganate. My fry tank is on A overflow system with my planted display tank to keep the water perfect. Anyone have any ideas?

[DISCUS STU]

I'd try posting this to the "Disease" section. This is typical in adults and I've seen it many times. I've always thought of it as a bacterial infection of some sort and it's gone away with water changes and some antibiotics like Kanamycin Sulfate but I'd try to get some other opinions.

[Snakeeyes]

Ya I'm looking for suggestions as to what it could be. I was suggested to treat with parazipro for a few weeks strait but these are the only fish affected in the system no others are showing anything like this
Sorry for posting in the wrong spot