Hyperpigmentation from Microdermabrasion and Glycolic Peel?

I spent a couple of hours sitting in the sun in the garden a few weeks after my last Microdermabrasion and Glycolic Peel. When I came in, I had a large mottled brown patch of skin on both cheeks. I returned to the clinic where I had the treatment, and I was told it was hyperpigmentation caused by the sun. I've googled microdermabrasion and realized that this can be a side effect. Did the treatments cause the hyperpigmentation? The clinic have sold me a further 6 microdermabrasion and glycolic peel sessions to restore my skin colour. So far I've had 3 with little effect.