julii cories acting weird

My fish are dying off in the same fashion as yours. A tiger barb, 4 gourami's, bala shark, and lemon tetra's. They appear to be fighting to stay afloat at times, other times they sink to the bottom and rest, and when they are moving they bang into the side of the tank. See my other post askinf for help.

I am hoping to find something out real soon because I am losing one a day at this rate.
 
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