Fixing some bleach mishaps?

Hi there,

I recently bleached my whole head with the aim of going some kind of ash blonde. I had about three inches of dark brown regrowth and faded ginger hair that goes just beyond the shoulder. I used 20 developer on the length and 30 on the roots. The ginger parts came out to be a beautiful buttery blonde, but the regrowth...

Turns out two (two!) packets of bleach wasn't enough for my thick af hair and now I have several patches on my roots where the hair is still brown or dark blonde. What's worse, one of the patches is at the front of my head and very very obvious 🙁 it kills me everytime I put my hair up and I've got a huge streak right in front.

My question is : do you think I should go back in and bleach the dark spots after a week or should I just put toner on my hair and bare it a month or so before trying again? And what strength developer should I use and for how long? I'm super paranoid about keeping my hair healthy, so I'd love to hear what you guys think is best.

p.s. I can't post an image atm because its night, but my hair is about a level 8/9, the spot in the front is 6/7, and the ones in the back are level 4. if that helps at all!