Colour leakage

You can try clarifying shampoo, stripping shampoo, or like you said, more bleach (all of these only on the bangs so you don't damage the black parts). Clarifying shampoo is any that calls itself clarifying, stripping shampoo is your regular shampoo mixed half and half with baking soda. It should come out gradually, bleached hair is really porous and nothing sticks to it very long, if the shampoos and bleach don't work immediately, time may just do it.