Ok, well here goes, i got up 2 days ago to find a dead cherry barb in my 38g,

there was no obvious signs of diease or fin nippng there was a small bruise like mark on his head. Well needless to say he was sent to fishy heaven and then i found 1 fry in the tank, (quickly saved it into the breeder net).
Later that evening i was watching the fish when i noticed i could only see 4, when there shud be 5, after about 10 mins of searching i found her laying on her side at the bottom of the tank under a plant, of course i immediately assumed she too was dead, it was only as i scooped her out in the net that i noticed she was still breathing. She has been fin nipped i think as her dorsal fin is gone, half of her tail fin is missing and her fins on the side appear nipped too.
I placed her in the breeder net for safety from whomever is nipping at her and added some stress coat, as soon as i had done this i found another fry in the tank, both fry are now in a breeder trap so that my cherry can stay in the net. She continues to lay on her side and does shift herself towards food when i put it in there for her, but all the time is staying on her side at the bottom of the net.
Yesterday i found an additional 13 fry, so i assume it cant be a problem with my water parameters of which are
ammonia and
nitrite 0
nitrate 5
pH 7.2.
I thought that all of the fish i have in the 38g were peaceful community fish

what could have caused the one to die and for her to be this bad, the other barbs seem quite lethargic too, they are not darting everywhere like they used to, i have not seen anyone showing signs of aggression to anyone else, could this be fin rot not nipping.
Any suggestions are gratefully recieved, sorry to have gone on so much but this has been bugging me for days with no-one to talk to about it.