can I save mixed nutrients?

If I pre-mix a couple gallons of nutes, can I save some of the mixture for a few days or does it go bad?

I'm starting some hempy buckets and I need such a small amount of nutrient mix at this point, that I find myself mixing it by the quart and it would be way easier in larger quantities.

It depends on what you're using.
Most organics shouldn't be stored for long after mixing, but some can.
Most chem ferts are OK to mix and store, but check your label just to be sure.