He needs sugar in his vitamin water! Please give him sugar!! If he won't drink it, I will even syringe it (no needle) into their beak a bit and it perks them up. Mix up his whole water bottle with the electrolytes and then add a teaspoon or so of sugar into that. I even will syringe up yogurt and put that down their beak just tiny drop at a time. He needs some extra TLC or he could go down hill quickly! I have learned FIRST hand here on shipped birds.
ETA: OH and check his vent area and look for mites just in case. Give him a good dusting of Sevin Dust if you do see any bugs.