there is always a chance of them being het for something, but without any visual markers, the chances of them having matching het genes are slim to none. For example, one could be a het albino and one could be a het axanthic, even if those genes were passed on, nothing visual would come out of it so you still wont know for at least 2 breeding seasons to try and rule out any genetics. In my opinion, it isnt worth breeding them for a slim chance of them having something special, because in all actuallity, they could just both be normals in the end anyway.