Bristlenose Pleco Question

#1
I have had my BN Pleco since the beginning of February, or what I believe to be a BN pleco. ATM it has 4 very small whiskers and has a coloring like this, but of course, with not as large of a quantity of whiskers. I think it either is a female, or just hasn't grown its whiskers in yet.

So my question is, how long should it take for a BN pleco's whiskers to grow in?