I had a rash similar to cold sore appearing and within day 2-3, the rash turned into a deep brown hyperpigmentated spot. I did two rounds of pico at a derm office and have seen no improvement. I am Fitzpatrick type IV and have been using tretinoin 0.5% for a while and added HQ 4% about a month ago. What do you recommend? I see no change in pigmentation at all.