Spotted Bush Fish Growth

[Deroplatys]

I brought a pair of bush fish several months ago at the same size. At the moment though one has grown twice the size of the other one. The smaller on is also much darker, is it sexual dimorphism?
When ever i feed them i always make sure to the little one gets some which it does.

 

[mattlee]

i found that mine grew faster in warmer water with plenty of meaty foods while they were in with some discus. if you only have 2 then there might be a dominant fish. even thought they arent aggressive they can be slightly towards their own species. the smaller one thats darker may be a little stressed, i would think about getting 1 more
they also need plenty of plants to hide in to feel secure.