The main thing you need to do for your horse is be consistent. Doesn't matter whose advice you take on the nutrition and feed, ask 10 horse people and probably get 100 answers and we all think we're the best/right. Switching from one thing to the next to the next isn't going to work and might harm.
So, if you choose to feed a certain product, say Strategy, then feed the same amount at the same time every day. If you choose to do the psyllium ( I use Metamucil 1/2 cup/day for 7 days each month) then do that once a month consistently. Make sure she has access to a good forage, I like free choice Bermuda grass for my horses but it's a regional thing. Leave her plenty in front of her 24/7. Don't keep adding and subtracting a bunch of supplements, pick something and stick with it. Give everything at least 3 months to begin to show some kind of change. If you like the way it's going, give it 3 more months and re-assess again.
Another KEY issue is to WEIGH your feed. I don't mean the grass hay, that's free choice, unlimited. But any concentrate whether you choose to feed a product like Strategy or Nutrena or Blue Seal, read the tag and feed for what you want your horse to weigh, not what she weighs now and then make sure you weigh it every single time you feed. So, if you're feeding 7 lbs of something/day, then weigh out 3.5 lbs of it morning and night, or 2.3 lbs morning, noon and night. It's the only way to be sure she's getting the right amount of whatever your feeding.