It sounds like the anti-scald adjustment for your faucet is adjusted too far to limit the hot water in the mix. Check the instructions your plumber should have left with you for the faucet. Or if he didn't leave you any, call:
Kohler Customer Service:
800.4.KOHLER (800.456.4537) or 920.457.4441
It really isnt that hard to do.
Good Luck!
Dodgeman