Ive had this problem before. I would remove the shrimp, if they are touching it, and put them in a seperate tank, then put scrape as many as you can off the plants and tank. They are related to the jellyfish, and do sting. It wont hurt you, but it will probably hurt the shrimp. I am not sure what killed the hydra when i had them, but they all went away. So i cant help there.