They could be heckels or browns it's hard to tell from that one picture and the awkward angle of the fish. They also appear to be only about 3 inches in total length so they wouldn't have their full striations yet at that size. I'll need better pictures and more information such as how big are they, and how long have you had them? If they were recently imported it's normal for them to be thin, but with good feedings they will put on weight quickly.
Jerry
It's just a box of rain