Moderate Acne or...?

I was told by my doctor my acne was moderate about 8 weeks back and I was prescribed a course of lymecycline having been on oxytetracycline for some 12 months during the course of which my acne improved and then declined again.

I also began using a red/blue light 5 weeks back. The acne on the front of my neck near my jawline and below my ear has been the most stubborn. The lumps were small and pink/red but concentrated in a small area. They were also very itchy. For the above reasons I suspected I may be suffering from a form of folliculitis (see:

I began using head and shoulders anti dandruff shampoo on the affected area around a week ago. From about 6 weeks into the antibiotic course my skin began to show signs of improvement.

My questions are: if oxytetracycline became ineffective is it likely the lymecycline has caused my clearance thus far? If I am indeed suffering from folliculitis does anybody have any theories on whether red/blue lights can kill the yeast in hair follicles that causes it?