
Ok, I neeeeeeeeed help. Yesterday I got some new fish for my 20 gallon tank( 2 molly fry, sucker - died, and 3 neon tetras). I just looked in my tank to see that one fish has white stuff on it's eye, one has junk on it's lip, one died, and one has tail rot!!! I am taking the sick fish to petsmart and to get my water sampled. I don't want any of my other fish to die, or get sick. I have a spare 10 gallon tank but none of my family wants to set it up

. If someone can give me a few tips that would be great!!!
been running over a year
nitrate: btw/ 80 and 160
nitrite: 0
pH: 6.25
carbaonate hardness: 50
general hardness: 140
Stock
3 neon tetras
2 harlequin rosbaras( both with fin slits but one with lip junk)
2 molly babies
1 platy( small slits in fins)
3 black skirt tetras( all with small splits in fins one with white stuff on eye)
1 flows orange and black fish(has fin rot)