my nearest pets @ home is crap, i went to one in manchester which was good though.
with the rams i wouldn't take any back i think there is a chance that the top picture is female, how big are they?
if you take them back they will only be able to guess what they give you anyway, they seem to be ok together from the picture, what are they like, 2 males would fight.
in the bottom picture the one on the right has a longer 3rd ray in the dorsal fin which would indicate male in most cases, give them a bit of time and see what happens.
Dave