Yes they are the Api bottom feeder pellets with shrimp. I am going to be switching them to the Fluval bug bites. I also make sure they all eat at feeding time and the one with problems is still eating good. Today I noticed when looking at him he does have a weird slime that looks like its ghosting off his fins, I think Byron was right about the ick so im doing what he suggested about raising the water temperature to 86°f to kill off the ick.I tend to agree it is mainly a nutritional issue.
For some reason Tetra flakes often occures in Cory-issues. I suspect that not the amount of protein is the issue but the kind of protein is (protein isn't simply protein but depends of the amino acids involved).
There might be a lack of other miberaps / vitamins.
Are the API botomfeederpellets the ones with shrimp in them.
Variation is key and certainly in case of wildcaught fish.