Why are my albino bristlenose plecos like this?

In my 40 gal, 1 of them is dul and the other one is bright and good looking. I the bright one a male or just the dominant one? Also in my 20 gal thy both seem to b the same color, does that mean there both males? On of them has white dots on the edge brim of it's tail and the other one doesn't, it the wilhite tip one a boy? Iv only had them for about 2.5 weeks so they haven't grown any whiskers yet