I've gotten 3 male rosy barbs for my newly cycled tank a bit over a week ago (the shop had no females). After a week I noticed that two of the males have the spots near their tails much duller than the 3rd one (which is also the largest one). I googled it and the only theory I came up with was stress due to insufficient school size. Now I finally found where to get the females, bought 3. The smallest male got back his normal coloring, but the middle sized one is still duller and his spots sometimes disappear almost completely. The change in color can be quite rapid, like, one minute he can be nearly blank, 10 minutes later his spots are only slightly lighter than those of others. He is active, eating well, he isn't bullied (other than regular displays and chases that happen between everyone without exceptions). Is this a problem or nothing to worry about? Tank is 30 gallon, cycled, planted (although plants are still small), no other fish, nitrates at ~10 mg/L, GH ~15, KH ~12, pH 7.2-7.5.