If they are "normal" ones then this normally means common plecs although that's a very bold claim to make. There is no sure way of saying what they are unless you were able to post a pic of them on here...
But..
If they are commons and they haven't grown for years like you said then the reason for that is they are already likely to have become stunted due to being in an unsuitable tank size.. This is where the fish stop growing on the outside but their internal organs continue to grow resulting in deformity and early death in most cases. Can't see it being to pleasant for the fish in either... Again... This is not a certainty, just what would tend to any fish kept in too small a tank.
A common can get around 18 inches in length whist sailfins get even longer... Closer to 24 inches (2ft)