At the beginning of the year I bought 2 common plecs. Since then I've been feeding them like nuts, but they won't grow past 4~5". They have coloration that looks like it came from a dinosaur. And it changes color depending on lighting. This is almost exactly what it looks like. I have 2 in a 55G and they don't mind each other in the least. They've been this long for several months now while my oscars get huge. What could they be?