Help! My fish are dying?

I have checked the water chemical content (ph, ammonia,...) and they are all fine. I after did a full out "Ick" treatment because I thought I saw some white dots on one of the fish. And now all my fish are still dying, i just lost 3 Neon Tetras, a Glass fish, and a Platy lately in the last day! I enjoy a 20 gallon freshwater tank, i use aquarium salt to reduce stress and own a plant light installed which i turn on 12 hours a day. Yes the bubbler is working very very well and a very good chemical and biological filter. I also have be doing water changes because of their deaths! Nothing help! Any Ideas?
Hmm. Well, it's possible that you use too much salt. It's also possible that you didn't cycle the tank, or that they be being overfed. It is also possible that you introduced a sick fish into their environment. Good luck!
All you can do is if you hold another aquarium quarantine the sick ones carry on doing water changes, to try and return with everything under control.Try turning temperature up for a couple of days or until you see real revival.
What ich treatment did you use
Answers:    how the tank temp?
Did you add chlorine remover to the freshly added water?
whether you did this and all you mentioned above that means you have a bacterial infection and you call for to treat it asap

"I suggest is CopperSafe by Mardel Laboratories. If you use nothing else use CopperSafe. It is a very fitting all around treatment and can be kept in there for a month. I resembling it a lot and have had angelic success with it. CopperSafe treats for the following diseases: Ick, Flukes, Anchor Worms, Velvet/Protozoan Diseases and other freshwater parasites. In amalgamation to treating these diseases it also aids in stimulating the appetite in sick fish."
Turning the flimsy off might reduce their stress. Also, some bacteria thrive contained by warmer water, so keep that contained by mind. It might not be ich, it could also be an internal parasite that you cannot see.
Turn the heat up!

A good 2 degrees for for a moment while.

By the sounds of it you have a community tank and most fish will tolerate the higher temps.but the germs wont so give it a try.

Also do a 1/3 water change to oblige dilute whatever is in there making them sick!
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