Blackheads after Cosmelan - what could be the cause?

Hi, I had cosmelan 4 weeks ago, I have noticed blackheads on my forehead, nose and cheeks since having the treatment. I have been applying the cosmelan 2 from around day 6 of treatment after my peeling stopped. I was applying it twice daily but was getting a lot of sensitivity so now applying it nightly. What could be causing the blackheads? Excess oil caused from over exfoliating? Thank you!