We are in a similar situation as you. We decided on 4health as well. Our breeder is also a vet and when we inquired with her she said that a lot of her patients are on 4 health and doing quite well. She chooses to feed a mix of Raw and a much more expensive brand that I can't find locally. She also buys in bulk so it's probably cheaper through the vets office..... Just saying.
We are transitioning our pup (8 weeks and a couple days old) over to 4Health and so far so good. Stool looks pretty good, he seems to like it. I have nothing bad to say about it thus far. We are mixing in a little bit of raw as well.
I'm not sure if that answered your question but is the best feedback I have.
Are you transitioning to adult formula? My breeder feeds all their pups adult formula as they state it is better the grow GSD's slower to prevent bone issues, etc... My pup seems to love the food and she's very healthy.
Uma - Red & Black Female GSD
Lili - Red & Black Long Stock Female GSD
Molly - Tan & Black Female Yorkie Mix