See, the reason why I think Ash had a tough time with Charmeleon and Charizard is because of that Exeggutor episode that Charmander was in. If you kinda think about it, maybe both Squirtle and Bulbasaur said something to Charmander about Ash not liking it. As it evolved, Charmeleon was like, "Heh, I'm already powerful. If Ash doesn't like me that much, so be it. I'm a more powerful being than he could ever handle..."
Even as the story progressed, Charizard was becoming more of a bad*ss than Charmeleon was and it costed Ash to lose during the Indigo League...
I don't think that Corphish should evolve just yet. Its character is still coming into view like the "Once in a Mawile" episode. It seemed to be attracted to female Pokemon like Brock is to girls.