Feed, feed and more feed

Nina was on an escalating path to manic for the past few days. I didn't notice at first because I was riding her each afternoon as the thunderstorms were rolling in and I just wrote her spooky, reactive behavior to the weather.
Saturday and Sunday it was still, quiet and HOT. She was a lunatic in the round pen, attempting to gallop, stretching her neck out for more and more speed. Trying to stop her just resulted in screaming stops and a quick rollback to zoom off the other direction.
When riding her a spook turned into an hour of trembling and bulging eyes and veins.
In her pen a misstep on my part resulted in her attempting to climb the fence and then staring at me with bug eyes and much snorting.
At that point it FINALLY occurred to me that she was acting like TB on crack. The classic symptoms of a TB being fed a high sugar food that they cannot tolerate.
hmmmm, I had just increased her pellets 2 days before this behavior began. The barn feeds a brand name, cheap pelleted feed made of 'various distillers grains' which could very well mean that there is corn in it.
I had hoped to be able to let the barn feed her, that is what board is for, but they don't offer any alternatives and it appeared that the feed was the culprit.
I arranged for the pellets to be discontinued on Sunday and on Monday she was already a little calmer. Today (Tuesday) she was a loon again, including sticking a leg through the fence while being lunged and ripping a shoe off and putting a hole in her other fetlock.
And there was the remnants of pellets in her feeder. I used this bucket for water the day before so she was fed the pellets last night or this morning or both.
I got the feed issue straightened out with the barn, they are going to feed a small amount of whole plain oats (that I supply) and NO pellets. I may have to break the bank and buy Nutrena XTN, which I heartily endorse for reactive horses. Very high fat, no corn or other sugar.

This is not the first horse I have owned that made an issue about certain foods. Scotty lost his mind on the tiniest amount of alfalfa. Nina eats alfalfa with no effect but obviously cannot tolerate whatever is in these pellets, which is a popular feed locally and a reputable brand.

I have to wonder how many problem horses are horses with a food problem. They cannot tolerate certain feeds and either no one thinks to change the feed or they are unable to find a feed that does not have adverse effects. And the less rideable a horse is, I think the less people are inclined to spend money on expensive feeds.