From the picture you posted, the goldfish DO look stunted. A good indication of their stunted growth are the size of their eyes in comparison to their body. IMHO, you as a person should not have fish, as it is quite obvious by your blatant disregard of other people's perfectly sound and helpful advice, as well as your continued denial of the way you are treating your fish.
Anyways, back on topic in regards to your original question and in response to some of the other posts.
No, you should not get an algae eater; the main reason being your tank is already overstocked.
However, contrary to what many people say about incompatibilities between goldfish and other tropical fish, this is not necessarily true. Although goldfish are natively coldwater fish, I personally have had great success in raising them in tropical temperatures with tropical fish AND tropical plants. Its a long story, but I currently have five 8" goldfish living very comfortably (and peacefully) with: 7 adult Angelfish (2 of which are a breeding pair), 6 cories, 11 otos, 4 SAEs, 12 black phantom tetras...all in a 135gal heavily planted tank. In fact, all the fish seem to be quite happy; both the cories and goldfish have spawned numerous times in the tank.
I originally started with the 5 goldfish as feeders I bought from the LFS for $1 each. They were all placed into a 20gal tank, and within 6 months they grew to 6". It was obviously overstocked, so they were temporarily moved into a 30gal for a little while before joining the 135gal.
Honestly, either give the fish back to the LFS, or get a larger tank.