Okay never mind overstocked, the stocking is pretty bad, I say dwarf gouramis should have at least a 20 gallon for 2 but they shouldn't even be together, 2 male dwarfs will fight, as will the gouramis and betta, male guppies and bettas are a bad idea as guppies look like another male to the betta, I'd say rehome the male betta and one of the gouramis and keep the;
1 Dwarf Gourami
5 Male Guppies
1 Apple Snail
Thats pretty much your stocking limit, maybe room for a few ghost shrimp but thats it.