You may want to simply go out of the E4, accept defeat once, and train(I got all my guys to 60 before the E4, and had a Gogoat, which made Siepold a breeze, except for the Gyrados, because grass isn't super effective to him, I had rock type moves though, so it was still easy.) So, either, quit and train your ampharos more, and definetly get the amparosite if you don't have it(on a small island given to you by a man on the way to Sea Spirit's Den, or, if you don't want to give up, teach one of your 'mons a strong rock type move through TM.