At that age they should have similar tails and there is no way to tell if they are a male or a female. They do keep their tails on either side or straight down(which is fine). Pretty sure there is nothing wrong but you should post some photos just in case if you are worried
Seems pretty young to tell but from my past experience, i'm leaning towards female because the guys seem to have a long and skinny tail while the girls are short and stubby at this age