What to Feed the Horses?

Five years ago we were giving each horse their own special grain mix, supplements, every shot the vet recommended and all the suggested chemical wormers. They were not very healthy, and as I began to do research, I gradually cut back on the vaccines, stopped the wormers and just had the horses checked for worms occasionally, and stopped giving grain and supplements entirely. The past three years, they have just been on pasture in the summer and chemical-free hay in the winter. Chance got some organic oats or sunflower seeds when he got too skinny, and I left Redmond salt, kelp and diatomaceous earth out free choice for them. They have been much healthier on that simple diet than they were before, but I still thought I could do better. I had taken the bad out, but I wanted to put some good in, so I started researching. This is a work in progress, but here it is what I have come up with:

Basic feed is still grass in summer and chemical-free grass hay or grass/alfalfa in winter, with free choice salt, kelp and diatomaceous earth. They get their "grain" mix once a day.

Chance: A 27 year old Thoroughbred cross, he is always skinny and needs some help keeping weight on.
1lb. organic oats (I get them from a co-op for around the same price conventional oats would be at the feed store)
1 1/2 cups chemical-free sunflower seeds
2 oz. Fertrell Horse Power (a blend of vitamins, minerals and probiotics)
1 T kelp
molasses for palatability

Shady, Phillip and Snickers: mid-aged horses that are easy keepers (don't have trouble keeping weight on), as you can see in the picture of Snickers
1 cup alfalfa pellets
1/4 cup sunflower seeds
2 oz. Fertrell Horse Power
1 T kelp
molasses for palatability

Migdalah: Two year old not being ridden yet.
1 cup oats
1/4 cup sunflower seeds
2 oz. Fertrell Horse Power
1 T kelp
molasses for palatability.

The horses were on this diet for about a month. Two weeks ago I stopped the "grain" temporarily since I have been busy and will be leaving town. I will definitely resume when I get back after the results I saw after just a few weeks on this diet. Wow! I've noticed the biggest change in Snickers; he is all glossy and dappled out.

Snickers in July, just before starting this diet

Snickers in August, after less than a month on the new diet