Do searchs on these forums. All your questions have been asked before. But no, 10-x-x is too much nitrogen and will make the plant too green and harsh to smoke.
its not ideal, but its better than nothing. what were you using to veg with? mj (contrary to a lot of uninformed opinions around here) is best grown with about the same formulation throughout its life cycle, veg and bud. 3-1-2, 3-1-3, 3-1-4 are the ranges i shoot for.
if your plants are healthy with the fert you were vegging with, you should keep it.