Well i know the the green tiger barb is full grown i believe. The rosy barb (2.5)now could double in size. So will the firemouth. Red tail shark (3'')may grow a little more.Gouarmies another inch which would make it 4''. My other tigerbarb is about 1.5'' now. Pleco about 3'' but will grow alot more. So the molly and betta will have 2 go soon along with red lamp tetra.
you definitely need to cut down on the amount of fish, I'd look for a new home for that pleco. If you get rid of the shark and the gouramis, maybe then you can look into another cichlid, or try to pair up your firemouth.