I've never fed clover of any kind, its a legume like alfalfa, but to my knowledge alfalfa is the safest legume to feed horses. What little I know about clover of any kind is that its very important that its put up properly to avoid mold, the mold in clover hay is more toxic to horses than mold that occurs in alfalfa or grass hays. [i don't know if it was red clover or another type of clover, but a friend of mine in college ended up putting a horse down after it ate poorly put up clover hay and got sick. Its been over 20 years, so I don't recall the details, only the end result.]
I think I would go with timothy cubes or timothy/alfalfa cubes to stretch your existing hay supply over the hay in question. [Perhaps if you know for a fact its been fed to horses with no issue, it might be worth considering, but I don't think I would.]
I'm low on hay, and just barely getting the horses out on grass, so I've been stretching my hay supply with timothy pellets. They go out for grass for about 1.5 hours in the morning, come in to drylot, get a scoop of timothy pellets and then get their hay for supper. Perhaps not ideal, and I've just started this routine, but so far, its working fine. The yearlings go out longer on grass, as they aren't air ferns, yet. The two geldings are getting more time on grass, but they've had access to grass longer than the mares (just logistics of my set-up).