I know that RTC grow reguardless of the tank size but when they are smaller ( about 4 inches) what should i expect?? I have 1 RTC that ive had since it was and inch and grew slowly at first and then sped up.. but then i got another RTC and it was 3 1/2 in when i got it and it doesn't seem to be growing much and eats about half of wat my other one eats??? is this normal???