Since both dogs had very similar blood results I also think diet is likely. I hope I haven't been a bad dog Mom and been overdoing it on the meat. I am not sure about the extra D for dogs or what the recommended dose would be. I could look into that. You are right that being further North we humans do need to supplement vit D and we take 1000 IU but I have no idea what dogs require.
I will continue with the crushed egg shell and see if I can get more info.
Thanks for your thoughts!