i don't think you have root rot, but i do think you have very heavy dense soil that doesn't drain well, and you've been overwatering, so your roots are probably a little stunted. repot with some perlite and/or coarse sand added to the mix, at least 25 to 30%. then start letting it dry out good between waterings. you want it to be DRY 2 inches down. not damp. the pot should get very light. thats how i tell when i need to water, i just grab the pot and see how heavy it is.
after a week or ten days it ought to start perking up. have patience. don't love it to death, lenny.