What did this do to my hair?

I had my hair dyed dark brown, I didn’t really like it and I used a diy hair color remover that consists of head and shoulders and vitamin c tablets (yeah I know, but I was desperate). I put this twice on my hair and the color did fade significantly but it also left my hair super dry. Whenever I wash my hair now I can’t even run my fingers through it, it’s like it becomes a huge clump as soon as it comes in contact with water. When I blow dry it it appears soft and knot free. Can anyone explain what happened here?