Important criteria in fry growth......

I really cannot explain why my fry seem to be slow growers of late?.... I do water changes.... I feed brine shrimp..... (only thing not observed is temperature)..... I do not have a heater in the tank and I'm not monitoring it at all.... just assuming that at around average 26 deg C it is fine.....

Can temperature alone contribute to the slow growth of my Orange Chromide fry??... They are around 2 weeks free swimming.... but look like 5 day olds....

They were accidently bred in a 4" depth 5ft tank which leaks if I put more water in and I cannot put a heater in.... Do you think this alone would affect their growth rate?....