Within the past year I noticed no matter what bleach or developer level I use my hair won't lift more than 2 levels. I'm a natural level 6 and used to be able to get to platinum in one application but now I have to do 3 applications on my new growth even with 30 or 40 volume developer and leaving the bleach on up to an hour with a cap or with heat. I've tried matrix, pravana, and recently switched to tigi true light after hearing good things but still the same issue? The lighteners work perfectly fine on other people i've used them with.