After some quick testing in org
Hot =>efflor : 983
efflor : 655
efflor => rejuv : 3486
rejuv : 3486
hot => rejuv : 3937
Looks like it will benefit from mastery but won't trigger mastery.
Hot => walk into efflor : 983
walk into efflor => hot : 655
So you need to have the hot before you walk into efflor to get the mastery bonus.