So, not all of the bleach was gone before you rehighlighted?

If so, that's the problem. Bleaching your hair is one of the worst things you can do. It strips your hair of it's pigment, leaving it very thing and fragile. Your roots didn't react poorly because it's new growth, or virgin hair. But your ends, which were already very porous and frail, were processed again.

Honestly, there's not much you can do without going to a salon and having them help. The best thing would be a hair cut to get rid of the damage. Or just wait it out. Eventually, and it's a long eventually, your curls will come back.

I'm speaking from experience. I love being blond. My curls do not.

In the future, if you want to rehiglight, just do the new growth.