'Folgers horse feed' didn't come up in google, so have no idea what the 'sweet feed' & senior is, let alone what size plastic jug. What fruit? How much? How often? What type hay?
All I can speculate from what you've told is that as 'sweet feed' is basically junk food for horses, that's not helping. IF the senior feed is also high starch/sugar, grain based, that's probably not the best either. Depending what fruit & how much, a lot more sugar there. If high sugar & only feeding 2-3 times a day that will also effect the gut more negatively than if fed little & often. And possibly her teeth, worms, ulcers(from the junk food), IR or cushings... has she been vet checked? Need much more info to do more than guess, as you can see.