You can run the carbon that will help take toxins out of the water. If you do a water change I'd do no less than 5g as your tank is small that would work out to about 20% which is ok. Was the stability stuff called cycle as that would help with the biological filter also or was it Super Bac Aquarium which will also help your bio filter IE:Live Rock replentish after a crash. It also removes ammonia. But for now stop addingand sit back and watch the fish see if they eat anything and if there breathing settles down a bit you know you are going in the right direction.. as I said before you can lower the temp a couple degrees and add a air stone this will help the fish and the stress turn the lights on the tank off, room lights are ok for now till you know what is happening.

Bill