Weird new hair texture!

I was at the salon 3 weeks ago getting my color changed from a light warm brown to a deep brown with a plum undertone and the stylist noticed that I had a section of hair that was really coarse and rough that we both hadn't noticed before and she thought it was strange.

Anyways the plum faded to a really warm red within a week so she had me back in to put a flat brown color on top of it to counter the warmth.
As she was washing my hair she noticed this little section of textured hair again and couldn't understand why it was there.
As she blow dried it she showed me exactly what she was looking at and explained it looked like it had been chemically relaxed and had this weird crimped, coarse look about it and it's extremely dry.

I've washed my hair tonight (first time since my stylist did it) and it's worse, it's probably only an inch wide section but it's really close to the parting so it's really visible and so coarse it's like wire.
It's not stretchy wile wet but rather weak to the point were I cut a strand off and managed to break it effortlessly in 4 pieces, so I'm thinking it's rather brittle.

Could it be because I did a protein treatment before both colors and my stylist used one too the first time she colored it or could it be because I had previously (as in 2 month ago) colored my hair with L'Oreal Casting Creme Gloss and she uses Wella Proffessional? Could the two different brands react to each other and if so why is it only happening to one section?

I've also had hi-lights in the past but I think most of those have since grown out.

How do I get it back to normal? I'm thinking moisture so I've put a little coconut oil in my damp hair and I'm gonna let it dry naturally.

Help please.