harvested broccoli turn bitter after 1 day.

https://preview.redd.it/hop4wysfey0e1.jpg?width=4096&format=pjpg&auto=webp&s=c4034d1bf543a57fef7426323dd794b4632f4718

https://preview.redd.it/wflc0aygey0e1.jpg?width=2304&format=pjpg&auto=webp&s=6f1b6071b3d72dbc6d0a4c6b59a7be89abc49f2d

After only harvested for one day, I found it had a strong bitter taste(still spicy), and look much saggy. What can I do nest time to prevent this?