Looks like it could be good, except for the corn, which I wouldn't feed, esp to a horse with a history of colic, as it's very high in starch & much harder for horses to digest. Guessing that if the horse colics on new rich grass, it's due to hind gut acidosis, which too much sugar/starch can cause.
Alfalfa is considered a generally good feed for horses, *if fed as part of a balanced diet*. It is high in calcium, which if not balanced can cause problems. It is high in protein, which can be problematic for some horses, and it is high in energy, so not generally that suitable for 'easy keepers'. I'd personally feed it at no more than around 30-50% of the whole ration unless advised by a nutritionist. So I'd probably feed a little less of that & more grass hay.
It is very important for a horse's digestive health that you change/add new feeds gradually. Hopefully they got by without it causing any issues, but I would have built up gradually to the maintenance ration over a 2 week period. It is also important, especially with starchy &/or fatty feeds, that horses get fed little & often & aren't subject to hours of hunger in between 'meals'. Unless they're fed in such a way that it takes many hours to eat their meals, I'd be feeding over more than 2 meals daily, especially as there is corn in it.