Get rid of the All Stock. That horse's coat is showing signs of bad nutrition. How much hay or grass does he get? He is a little thin.
We all assume that everybody has good pasture. MY elderly horses, now passed on seeded what had been a 3 acre field of corn in October, 1999, when we closed on our 5 acre property. It could NOW use some more grass, there is a LOT of clover in it, but my DD keeps commenting on how my 8yo QH looks SO much better (coatwise, specifically) than he did when we got him from the rescue several years ago. Their
pasture was 35 acres of crap.
I'm home today and grabbed some quick shots for you. You'll notice that my 3 have no winter coat left. I never brushed it off, they just went to 24/7 turnout and rolled it all off. They are on full pasture now, with a little bit of sweet feed at the end of the day to remind them to come home to me.
Long Arm of the Law, 8yoKMH gelding
Buster Brown, 8yo unregistered QH gelding (dam was a registered QH)
Warren's Cindy, 16yo KMHSA mare
I would suggest that you get the very best hay you can afford and feed your boy as much as he wants. Drop the supplements. Unless your Vet prescribes a supplement, we are ALL self-medicating with them.
Horses need low protein and lots of it. You are underfeeding your horse if you give them too much protein and supplements and supplant the hay that their digestive system needs with proper fiber to move everything along. It's like letting your kids eat candy before dinner. Their bodies will digest the candy and there won't be room for the green beans. =D