Hello, I have 5 red belly piranhas in a 125 gallon tank. I bought them 2 months ago and 2 of them are growing exponentially faster than most they are 3 times the size of the others. (Got then when they were a half an inch) I can tell the other 3 are honestly just not growing like normal , they seem perfectly healthy and I visually see them eat.? Also just now one had a slightly defective mouth and he got torn to pieces randomly after feeding time. Any explanation for them not growing the same/cannabalism/different growth. Thanks!