If in your preparation for hrt, you began to eat better, drink more water etc., it could possibly be that your body is going into a very slight elimination process. This is when the body is getting the green light to improve itself, and starts to detoxify.
The improvement of skin does in fact take place on hormone therapy, but (and I'm speaking in general terms here) 15 days seems fairly fast.
For me personally, I have severe forms of all three variations of Rosacea, one of which mimics acne (which makes it impervious to most acne medications). I am not sure why and even my dermatologist does not know, the hrt regimen completely eliminated all three of these at about the 3 or 4 month mark. Hope things clear naturally soon. Dani