I bought my orange mint plant in early May and it was beautiful, full, and green and smelled delicious. Soon after getting it planted in the pot I saw the leaves started getting the deep purple tinge that mint gets when it's stressed. I didn't worry about this because my other mints did that during the winter and all was well by the time I bought the orange mint. Well soon the discoloration spread and it is now way more purple than green and some of the leaves around the bottom of the stems have turned a super pale pink. There is new growth that's a perfectly healthy green, it still smells like orange mint, and none of the stems droop, but the rest of the plant is still purple.

What am I doing wrong? This is the only mint of mine that's acted this way. I've tried not watering it and then giving it extra water, keeping it in full sun and keeping it in dappled shade, nothing has changed for better or worse.