The Wellness Core might simply be too rich.
If you're going to feed kibble, and he has no known allergies, he'll probably do better on one WITH some rice, oats, or barley (see the other thread on the recent FDA warning on grain-free kibbles with potatoes and pulses). Those are all highly digestible. Potatoes and peas aren't as digestible for dogs, and they're being implicated in heart problems.
My first choice would be Fromm Gold Large Breed Puppy -- great company, known for quality control, and not too "rich":
My second, more economical choice would be Diamond Naturals Large Breed Puppy -- we feed a lot of this one in the rescue when we take on rescued litters. It tends to firm up their poop pretty quickly when we get them. It's not the best food out there, but it's a mid-grade food that's a good value, that agrees with "most" dogs.
For your other dog with anal gland issues, please check out Glandex as a supplement. https://www.glandex.com/
(It's available on Amazon too.) I have used it daily for several years for my dog with anal gland issues and food allergies. It's good stuff.
If you want to do raw but can't manage it, I agree that you might want to check out The Honest Kitchen as an "in-between" commercial option to kibble. It's not raw. It's dehydrated at a relatively low temp to preserve as many enzymes as possible. That's what I feed my allergy dog -- it produces ginormous, firm poops, which are actually exactly what you want in a dog with anal gland problems. They make several "just add water" dehydrated foods that are complete diets, and two base mixes to which you add cooked or raw meat. There are a couple of all life stages diets suitable for growing puppies (the base mixes are only for adults). For us, THK worked out to about the same or slightly less than a veterinary prescription diet. FWIW, I've seen THK's smaller boxes at Sprouts and Whole Foods, if you want to read the boxes and think about it. Sojo's makes a similar line of foods that's slightly cheaper.