My brocolli was being decimated by green caterpillars so i mixed up some pyrethrin snd sprayed them down along with my cucumbers and tomato plants for good measure. I go out the next day and now all my plants are burnt and dying?? Ive used this stuff in the past with no problems im very frustrated and confused. Theyve actually gotten worse since i took these photos

Pyrethrin and pyrethroids (synthetic substitutes) cause no phytotoxicity even when mixed with PBO: at very most they may cause some leaf scorch if sprayed in the hottest hours of the day like many other pesticides, but that's merely a cosmetic issue.

To be honest what I see in those pictures looks like some extreme form of leaf scorch. You can see exactly where the droplets scorched the leaves.
Which brings me to my questions.
1)What concentration did you use?
2)What did you put in the sprayer before using it this time around? If you used a spray bottle from a household detergent what was in there?
3)And last but not least, when did you spray the plants and how hot was the weather?

I would ask those same questions! Most problems with pesticides are caused by not following the directions carefully/ and /or not cleaning the equipment properly.