We have a mint plant in the back yard of the house we're renting. Earlier this year, I noticed that the leaves had yellow spots on them. I did some searching around the internet, and, of course, the first thing I came upon was mint rust info. So, I begrudgingly tore and cut the plants down. I let them grow back, to see if they would come back healthy, but, sure enough, the spots are still there. Before I take a more permanent step, I wanted to verify that it is, indeed, mint rust. I'm not sure at this point. I have yet to see any pustules at all or anything actually protruding from the leaves. It has just been these yellow spots as seen in the picture. Thoughts?