Keratin Treatment - First time was great, second made my hair like straw

(High Wycombe, UK)

I was really happy when I had the keratin treatment the first time which lasted approx 3 months. Then it started to look a little kinked again so I had the treatment a second time. This time it has not been at all successful, my hair feels and looks like straw.

I wonder whether it is the overuse of the hot iron straighteners which I am told are required to keep the product in the hair follicle.

Am now feeling I will have to have my long hair cut by at least 4 inches so its not been a success for me. I wonder whether it is only suitable for people with already course, and frizzy hair, so anything is an improvement.
Answers please!
Deborah