Do more water changes feed more slowly, so he (they) have a chance to eat up a fe
pellets before giving them more. Maybe a little less food and divide it into 2 feedings. That way it will not add too much all at once to the bioload.
Are you familiar with the nitrification cycle? The getting started article, link in my signature, is full of really good information. Very helpful to be able to check back on topics /issues.
Clean water is a number one best help for keeping fish well. Having a cycled tank / filter with a healthy BB / beneficial bacteria colony is #1 thing to do.
New to FW fish? First tank in a long time or EVER??? Need some info on keeping fish?
Start here - Aquarium Advice Article
FW Favorites right now Clown Loaches, any shrimp - SW Vase Red Mangroves