Kevin 'Coach K' Lee

City Girls breaking up their successful duo has turned JT into a savage -- her debut solo mixtape single "Okay" is now glittering in gold!!! JT posted up with her Quality Control label execs Pierre "Pee" Thomas and Kevin "Coach K" Lee on Thursday with her new Gold plaque from the Recording…

The man behind some of the biggest names in rap is giving Cole Beasley props for the track he dropped earlier this week ... but says there's a different NFL star who's got his attention. TMZ Sports spoke with Kevin "Coach K" Lee -- who runs the label, Quality Control Music, and has worked with…