Don't buy anymore dwarf gouramis (Colisa lalius) or any of their colour varieties because they are regularly infected with diseases that can't be cured.
Avoid balloon fish because their bodies are shorter than they should be and they regularly have internal health problems because of it.
I would stay with 2 keyhole cichlids because there are Corydoras in the tank. Too many bottom dwellers is never a good thing.
Black widow/ skirt tetras are renown fin nippers and should be kept in large groups. Even then they are an issue for slow moving fish or fish with long fins. If you aren't attached to the skirt tetras, I would get rid of them and get something more peaceful.
And as @Essjay said, increase the numbers of danios, tetras and Cories to at least 10 of each.
If you have one species of Corydoras, you could get 6 of a different kind to go in with them. Most of them tend to hang out together but they do need a group of their own kind. So 2 groups of 6 would fit in the tank.