Puppy diet variations/concerns?

[Phrixus]

So Phrixus no longer eats chicken thighs.

I've been staying pretty constant - a chicken thigh/quarter, couple boneless pork chops, some ground beef, some hearts/livers, Vit E/Fish oil.
Course I've varied it some - deer neck, pork ribs - but for the last three days, any time I've dropped a RMB chicken down - he won't touch it. Did he just have a bad experience with it and this will pass? He will continue eating MM or OM if I put more in, so I don't think he's just full. I'm gonna hit the butcher for some RMB turkey and pig today, but I also just bought 8 chicken thighs on a good deal, I don't really wanna waste it.

Also, should I have a higher RMB content since he is only 6mo?