Pond Frog

I had a tuff time finding the water hyacinths but I did. An apartment complex in the area has them and gave me a few. I grabbed 4 of them and they are about the size of a cantaloupe. For the first 3 weeks or so they seemed to be okay. During the past week I have been concentrating on getting our pools (3) and spas (2) ready for the Health Inspector. Anyhow, they now look dead? They turned brown with no color left in them. Should I try a larger quantity of them. These ponds are approximately 16-18" deep. I have some wire baskets that are typically used for tomato plants that I want to trim down in order to isolate the water hyacinths together and far out of reach of humans (somewhere) in the middle of the pond. What do you think or recommend? And thanks again.