I think that HK base mix is meant to be fed with muscle meat/fat only? If it has synthetic calcium, your dog might be getting too much? I've never fed the base mix so I'm no help. Bumped as I was hoping someone who feeds the base mix would advise.
Chicken is mostly bone. Talk to the folks at THK about that. That's a lot of calcium. They can run the calculation by their nutritionist. Just call them!
They told me a bit of bone is okay -- but I was talking to them about Primal Grinds with max 10% bone. Your chicken is much higher.
It's meant to be fed with meat -- muscle alone (like hamburger, ground turkey or deboned chicken), but muscle with a little (10%) organ is probably much better, esp. if you can get a good mix of organs. As the box says, you need to be feeding meat with EVERY meal -- not 3x week -- every time you feed THK, add some meat per the ratio on the back of the box, to create a complete meal. Don't feed THK alone, even a few days a week. (I'm not sure from your post if that's what you meant, but it sounds like you only give meat 3 days a week, so I wanted to clarify that if you feed THK 7 days a week, there should be an appropriate amount of protein 7 days a week.)
I add fish oil to it too. So did the rep I talk to at THK who fed it. Oddly, Dr. Harvey's similar base mix recommends that on the label. I don't know why THK doesn't.