Your best bet is to talk to your vet and hay supplier to see what your horse needs. Over supplementing can cause as many, if not more issues than not supplementing at all.
Most vets don't know diddly about horse nutrition, except what the feed reps tell them. Equine Nutrition is only a 1 semester course in vet school, and things have likely changes since then, lol. To the OP
: Enrich is on the low end of nutrient requirements and Omega Horseshine doesn't have high quantities of anything, so you should be fine feeding them together.