Yes all above is great advice.
I would only feed him the pea insides for a couple days. Turkey baster is a wonderful tank tool! If you don't have one, the discount and dollar stores have them for cheap. One fish keeping friend I have put a zip tie on the bulb to keep good suction. Cheap enough that if you need to wash out the inside you can snip it off and add a new one. also that way it would not get mixed up with a food turkey baster.
Maybe try using a small piece of filter media to be on top as the first layer in the filter to help catch the mucky stuff and throw that one away each week. When you throw away the filter pads they are the major colony of BB. Likely the combination of cleaning the tank before you left on your trip coupled with the usual overfeeding pet sitters caused the internal issues.
What I would do for my own fish...
Normal large pwc
I would also add Epsom salts magnesium sulfate, like for soaking a sprained ankle - available at the drug store or super market. No additives no oils, etc.
For the 2.5 G I would take 5 rounded tablespoons and mix it into an adequate amount like a cup, of really hot water til dissolved. Then add it to appx. double amount of cold water or ice cubes until tank temp, and add dechlorinator.
Remove the same amount of water as what you have mixed up and then over the course of the next day, add it to the tank.
This is a treatment amount of epsom salt.
initially add in 1/4 of the mixture, in two parts.
say half /part of the 1/4 amount then about a half hour later, the other half.
This just eases the water change for the fish.
In 8-12 hours... add another 2 part 1/4 amount of ES over a half to an hour.
Continuing until it is empty.
You can test for any water parameter issues during this time. I would keep up this amount of ES for 7-14 days at this increased level.
You can take more time later to make a concentrate of amount of water for amount of tablespoons of dissolved ES so it would be easy to dose it in for each pwc
. So the amount is per each .5-1G pwc
. As a fixed concentrate amount. Hopefully it will be easy for you to figure that out. I just keep it in a water bottle marked with a Sharpie.
After the 2 weeks if he is feeling good and acting good, I would do the normal pwc
and decrease the concentrate added to equal 1 Tablespoon per gallon. Try that for a week or 2 if he seems good, then just do normal pwc
and over time the excess ES will decrease and be eliminated.