Does he look like he is puffed out, like a pine cone? Do you ever give him a day off food? Doing a day of fasting, followed the next day by this can sometimes relieve them if it is constipation~ defrost a couple frozen peas in warm water, remove the shell, cut them, and give him a few small pieces.
The tank readings are important. A 2 gallon tank should be changed 50% twice a week, at the very least once, but again, monitor the nitrates with a test kit. API makes a good inexpensive titration test kit. That is where you should start. Stop adding "solution"..whatever that is. Just use Seachem Prime-get it next time when you run out to dechlor the water instead of whatever you have been using. Make sure you are only feeding him a good pellet, just a few twice a day. Like Hikari biogold, Omega One, or New Life Spectrum. Occasionally offer frozen bloodworms instead of pellets. Then once in awhile offer the peas.
