You are wise to remove the Convicts, a good decision.
Now to the Firemouths. You have three, do you know the genders? This is a gregarious cichlid, meaning that it prefers to live in loose groups, but obviously that means a larger tank as males will be very territorial when spawning. It might be best not to rock the boat with more Firemouths and work around what you have.
The species is naturally shy, and will be more "out and about" if it knows it has suitable places of refuge. The Convicts would serve to keep it stressed and thus in hiding, so this should improve with their removal.
Gourami are still not a good tankmate, as they are similar to cichlids--males can be very territorial, depending upon species. But we can consider suitable fish. Back a bit you mentioned a hardness of 7, is this 7 dGH? Or some other unit of measure?
Byron.