With your feed going in at 6.2 and run off at 6.8 that tells me your pH is a bit too high. Ideally I'd shoot for run off in the 6.3 - 6.5 range. Mi5 usually exhibits 3 different phenotypes, one of which is a runt. That could be what you have. Keep in mind that autos are still relatively new, only being around about 5 years now, and are not fully stabilized yet.