We just moved into a new construction house. Love everything but in the recent Seattle heatwave - I've found our master bathroom standalone shower doesn't get very cold. It starts out cold (like all do) but even with the lever all the way over to "C" it must be allowing too much HOT water through - as I get out of the shower sweating. It's a KOHLER fixture with one lever for "on/off" and another lever below it for temp. I tried to take apart the temp lever but couldn't figure it out. Any thoughts?