Internal parasite??? Help!!

[Lydia]

Hi all! This is unfortunately not a happy post. :-( my koi angel (Harvey) has been pooping white/clear stringy stuff and has lost his appetite. He has been shaking his head once in a while and seemed to be gasping fir air although not always at the top of the tank, but his mouth was constantly moving. His belly got really big but I had not seen him eat or poo in a couple days. I also noticed that he was either at the top of the tank or at the bottom. He never seemed to hang out mid level anymore.
I was told by lfs that this was an internal parasite and they gave me PraziPro. I treated the tank two days ago. I had not seen any signs of improvement. This morning I woke up and he was upside down dead on the bottom of the tank. None of my other fish have shown similar symptoms and they all seem to be in good spirits.
So a couple questions... What is it that killed Harvey, will my other fish get this and was I given the best meds to fix this? All water params are in good shape. I did have an ich outbreak due to buying an infected fish from lfs about 2 months ago. Treated with salt and heat after a failed attempt to cure with quIck cure. (I did remove carbon filtration for this med period and have them removed now for prazipro meding.) All seemed to be doing well until this happened. Between the ich and now this I don't think I can stand any more deaths. Please help!!! Thanks all. Please give all opinions even if not sure. That always seems to spawn discussion which I believe leads to the right answer. Thanks again!!!! Please help!!!

Freshwater 55 gal

 

[Matt68005]

hmm, did you mix medicines, cuz you should have changed some of the water in between treatments, charcol can loose its effectiveness over time.

 

[Lydia]

Oh ihave changed the water probably 10-15 times since the ich treatment. That was a while ago. I only mentioned it in case the problem now (internal parasite) stemmed from the ich issue which is an external parasite. I didnt know if anyone else who was "blessed" with the ich experienced anything similar once the ich was cured. It was probably 2 months ago that I would say i was rid of the ich. I change my water at least once a week.

 

[Lydia]

I also read to up the heat with medication. Now heat is about 78. Should i up the temp too???