Hydrogen Peroxide spray or bath is not a good idea for your plants mid flower, spaying that solution during veg or early stages of flower is fine. The biggest reason behind this is that hydrogen peroxide is highly highly corrosive and will literally eat away at your trichromes or wash them off. Not ideal. You'd be better off pulling the plants sooner.
As for using neem mid flower, honestly, compared to all the other stuff growers spray on their plants buds it's not as extreme and is just a good grade oil. Unless your PM situation is out of hand, only use neem oil with "the smallest drop of soap to emulsify the solution." Other than that, using any sulfer based fungicide is not a good idea.
Here is your best option to save your harvest.
Cut the infected plants if it is really bad infection already, there is no good done in spraying them down as this will cause the spores already in place to skyrocket around your grow room and infect more plants.
Go and buy a high quality hemp oil from your local grocery store or whole foods. Mix the solution to the same ratio as neem oil with a little soap to emulsify the solution. You can mix this with your Green Cure and it should do wonders for you.