are they getting enough sun?
do you have them the right depth in the water?

I believe they have enough sun. Not much has changed from where they grew last year.
One is on the bottom of a 300 gallon sunken Rubbermaid stocktank and the other one is on the bottom of another 300 gallon Rubbermaid Stocktank, which is sitting on the ground.
There is a ton of duckweed this year that I keep trying to remove, but it keeps growing back. No fish.

cather,
The duckweed is stunting the growth of the lily.
Go buy only 1 or 2 goldfish. They will keep the duckweed under control, and add fertilzier for your lily, it will grow remarkable then.

Thanks butterfly4u!