@420noob using the MTA mix, you can spray buddage all the way up to day of harvest with no ill effects.
It won’t do much good for any bud-rot though, so anything that has that, I’d cut n toss.
Ordering on Amazon today, you can have everything in a day or two, usually.
After you harvest, IF you decide to keep the plants and treat, instead of tossing. You can wash the buddage to clean out all the pests and stuff. At least then, it won’t be a complete waste of all your time and resources.