I would start with Fromm's "regular" Four Star (not the grain-free), as it's less rich (and likely an easier transition) than the grain-free Four Star. The Chicken-a-la-Veg might be a fairly easy transition from chicken-based Diamond, but the fish-based ones are also very easily tolerated by many dogs.
However, Fromm Four Star costs more than $50/bag (at least at my store..) -- I think the grain-in "regular" ones are just under $60. The grain-free Four Star is around $70 lately. Prices went up this year. Fromm Gold Large Breed Adult is about $50/bag.
I would stay away from the Four Star Pork & Applesauce with a tender-tummied dog. That one seems to set off some dogs' tummies, even when they otherwise do well on Fromm products.
Once you get them eating regular (with grain) Four Star, you can rotate into the grain-free ones too. The Hasen Duckenpfeffer is like candy to my dogs -- they LOVE that one.
Last edited by Magwart; 04-06-2018 at 11:24 AM.