Tissue response Ive never seen using Nd:Yag

Weird tissue response with Nd:Yag on skin type 4?

Hi all! I’m a relatively new medical aesthetician who does a lot of laser hair removal using the Candela Gentlepro max. Today I had a client who appears to be a skin type 3 but she never burns and always develops a deep tan even with minimal sun exposure and SPF. She is half Romanian and does not know where her mother is from as she was adopted, so to err on the side of caution I treated as skin type 4, ND:yag 18mm spot size, 16j, 10ms. She has also been burned by an ND:yag laser in the past.
Anyways, as I was treating her legs, 2 mins after i’d pulse there was relatively faint but still noticeable circles (the size of the distance gauge) that were a few shades lighter than her skin, all over. It looked quite shocking at first and she was quite nervous about it and since I had never seen this reaction before I did not know how to ease her mind.
I waited some time before continuing treatment and they did eventually go down, but I was so baffled as to why this would happen. I’ve never seen this tissue response and I’m wondering what could have caused this?

Edit: she said it was not very painful, has not been in the sun since September and has not used self tanner.

first, I’m not a laser professional, but I would use caution. It’s posible she may have some hypopigmentation issues afterwards, and we’ve seen several people here with this issue. I would wait to see what the result is before doing any more treatments.