Stretch mark question!!!

I have stretch marks that had turned silver/white with my first baby. No big deal. I did not get any new ones except old ones were a bit extended at the top as I carried my daughter higher than I did my son. I am three weeks postpartum and I just looked in the mirror tonight and they are all pink again, suddenly! They were not when I had my shower this morning. Could it be because I am feeling warm, or can they suddenly renew themselves, is it to do with postpartum weight loss? Just when I was feeling good about myself too...