Why are my platies and guppies dying?

[nathalie8_2000]

hello i have 2 tanks:
- 10 gallon with 4 female platies and 2 clown plecos
- 36 gallon with 4 male platies, 3 neons, 2 bristlenose plecos, 5 zebra danios, 5 pink glofish, 3 female guppies and 2 male guppies.

In the last month my fish are dying 1 by 1 and I have no clue whats going on, my readings are within limits, I do 30% water changes every week, i add water conditioner and some salt.
They start looking very sick, dont eat, their colors look very discolored and they hide a lot. I have treated them in a separate tank for fungus, parasites and even ick. I have also treated the whole tank, but nothing seems to work, they just get sick one by one, and after a couple weeks of weakness they just die. Right now i have a weak male platy hiding behind the filter and a discolored male guppy in the 36g tank. And in the 10g 1 female platy just died yesterday and another one is starting to look sick now.
What can i do?? I need some help here

 

[Coursair]

STOP adding Salt ! It does not evaporate and it's easy to over salt your freshwater tank. Do a large water change, with Prime, NO salt and see how they do. Your 10g sounds overstocked. or at least at the limit.

I had a customer who almost killed his 17yr old Goldfish by oversalting his tank.

 

[jlk]

Welcome to AA!!! I agree on the salt- a couple of large water changes with temperature-matched, properly conditioned water should help to reduce the salinity. What are your exact water parameters & what are you using to test them (liquid or strips)? Did you cycle these tanks before adding fish? How long have the tanks been set-up? What meds have you used so far? Some more info will help us to try & figure out whats going on!