Vivianna, here are my recommendations...
First, necrosis is a different thing than bud rot. Necrosis is death of plant tissues... leaves and buds, calyxes in buds, etc. If you've got a lot of necrosis happening before the buds are ready to harvest, this is a big problem – it probably means the plants didn't get enough nutrition in flower phase. Necrosis can also be caused by systemic nutrient problems, such as pH problems and lockout.
Big point here: necrosis can lead to bud rot, because the fungus likes to get started on dead material. BUT, it's possible to have necrosis without bud rot. Some of the photos posted here look like necrosis, not bud rot.
The distinctive evidence of bud rot is fuzz – fuzzy grey fungal filaments or webs. Again, here's a detail of what it looks like at the microscopic level:
HERE and
HERE. If you're not seeing this with your microscope, it's not bud rot... YET. Note also that advanced bud rot is very easy to see with the naked eye... it just looks like a fuzzy grey mess.
Now it seems you have reached a salvage situation – to harvest as much as you can and throw away anything affected by bud rot. I personally would clip off all buds that have a lot of necrosis or are suspected of having bud rot. Throw them away. For the rest of the buds, decide which ones are ready to harvest and harvest them. If you have definitely found evidence of bud rot anywhere on your plants, then the remaining plants and buds should be sprayed with a hydrogen peroxide solution daily. My recipe is 6 fl. oz. of 3% peroxide (or 12 tbsp) in 1/2 gal. pure water in a pump sprayer.
For any buds that you harvest, I recommend wet trimming, meaning don't hang up whole branches to dry – just trim the green buds. When you are trimming, look for bud rot and throw away any buds that have bud rot. When I trim I use a headlamp and high-magnification reading glasses. If you've got a nice-sized bud with only a little bit of bud rot in it, you can carefully salvage it. Bud rot hides deep inside buds, too, so be careful to inspect.
good luck!