Hairdresser bleached my hair causing it to burn & steam under foils?

Hi guys, not sure if you would be able to help, however here is my "horror story" / dilemma! I have no history of allergies, no hypersensitivities including dermatitis. Yesterday I got my hair done - touched up (ombre, with bleached ends). When my hairdresser of over 30 years experience placed the bleach (30 vol) on my hair with foils it got warm really quickly and then started boiling to the extent steam was coming off and burned my hairdressers hands.. Now fortunately she got it off in time before it did any damage to my hair. Anyway, she claims she has never had this happen before nor heard of it.. And she has used that bleach agent in my hair numerous times before over 5 years of intermittent bleaching.. She thinks s it is because I've been using purple shampoo regularly (..too often apparently) and there is a build up of "iron minerals" in my hair that reacted with the bleach... I just have a tough time believing my purple shampoo which is used for bleached hair could have caused my hair to start burning once bleach was applied.... Especially when I have friends with lighter hair than myself using it daily and bleaching 2 monthly. Does anyone have any thoughts??