I guess if it is a browned-out Pastel, look for more blushing than you would see in a normal, more yellow, or even the eyes, like several people have suggested.

If the female's head is smaller than your male's, and she appears skinny like you said, than she is probably underweight. Give your male's head a little squeeze for those fatty deposits on the sides. If she doesn't have those, fatten her up.