Well water at 300 ppm is prob full of lime calcium,iron in the form of rust & god knows what all,just better than no water at all.In your other post on this same subject,GRR,you didn't mention you had gone from ro to that crappy well water.Guilty of the sin of ommision bro'lol.
Sudden shifts in ph can effect plants in a neg manner.You got to be consistent in what you'r giving your plants concerning ph.