Fish Breathing Heavily And Red Line (Like A Visible Blood Vessel?) Help?

[jennesque]

I am posting this for a friend.. She's got a 35 gallon tank and has already had two deaths. Tank is established and cycled: 0 nitrites and ammonia, 5-10 nitrates and pH of 6.4 which has been steady for the past year. Temp is 79. It's a heavily planted tank and water changes are done biweekly at about 30%.

She has lost a female ram and then about a week later a platy.. Only symptoms with them was heavy breathing for about a day before they passed. It's about a week since the platy passed and she found her ram like this yesterday. It's breathing heavily and has this red line above it's gills.

Any ideas? She just started dosing Prazipro, thinking it may be some sort of internal parasites. Dosing started two days ago.

Tank mates are platies, cories, hatchets and a betta (who is a pansy).

 

[sophiamarvv]

I don't have much of an idea about the deaths of the fish other than: is there enough surface tension break? And also does she use any plant food in the tank? I experienced a bunch of deaths when I started using plant food for mine I believed because the heavy metals were too much for my fish.

But also, I did some research on the fish in that tank, and the ram and hatchet are the only ones who came up compatible with that ph. Just something to think of.