PLEASE CLICK! is my beta stuffed?

ok. so you may have heard that my beta ate the fin of my neon tetra last night. sadness. but anyways, now i think my beta may be overfed. he has this large bulge behind his gills. is he overfed? if so, how do i fix it when i have 4 neon tetras? only one of THEM is a bit stuffed! how much tetramin tropical flake food do i put in a tank with 4 neon tetras and one beta (normally, not in the crisis)?????? how do i fix my beta overfedness problem (is he overfed) if not, what do i do? he is swiming fine and is actually looking around in the gravel for food!