Willig's hives - what worked

Unfortunately, I can't say exactly what worked, but we are hive free and haven't seen one for at least two, and maybe three, weeks.
Willig is eating 1 flake of alfalfa for breakfast, 1 flake of local for lunch, and 2 flakes of alfalfa and 1 flake of local for dinner.
He's also gaining weight - he weighs the most in the whole time I've owned him, and he actually looks quite good with the weight on.
Then, for supplements, he is getting: Platinum Performance, Platinum Skin & Allergy, Riva's Remedies Equi-Derm (an herbal blend), Probiotics, and Strongid 2X daily wormer, only I stupidly was giving him a double dose for most of the last month.
He gets those am & pm, with a small amount of cob and oats.
I don't know if one of those things is working, or if it's the combination of all of them, but I don't care. He looks good, his skin is shiny, his tail is still dandruffy but not as bad, and he has less smegma on his sheath.
My plan is to keep him on it through early spring, and then let them all run out and see what happens. Next November, when the new hay comes in, I'll probably go ahead and try all of them, but at half-dose, to see if we start early if it keeps them from getting bad.
Also, he's been a much happier horse lately, and I think this spring he'll be ready to try turn-out in the grass!