Please tell me what is wrong with my broccoli plants!?
Those are broccoli flowers which means you broccoli has "gone to seed". Broccoli is a cool season crop that is grown in spring or fall. Here are some tips on keeping broccoli from bolting: https://www.gardeningknowhow.com/edible/vegetables/broccoli/bolting-broccoli-growing-broccoli-in-hot-weather.htm