Is it normal to get blackheads after photodynamic therapy? Suggestions?

I am a 39 year old female. Throughout my years, I've had bouts of acne flare ups that were always treatable. I started developing acne on my back and chest and more stubborn acne on my face in my early 30s. My acne is actually VERY mild, but stubborn. I tried several treatments and medications, but they didn't really have long-term results for me. Finally, I tried Photodynamic Therapy, and after the first treatment, I noticed several blackheads or clogged pores in areas I had never had them before. I just finished my second treatment and was horrified to see how many MORE blackheads I had developed again, in areas I had never had them before. Is this normal? I don't even want to go for another treatment because I fear it will only get worse. Any comments or suggestions would be extremely appreciated.