Water lettuce and water hyacinth not growing well

[Stevechi]

My water hyacinth and water lettuce are not growing. Leaves are turning yellow. What could be the problem?

 

[Phaewryn]

What zone are you in? When did you add them to your pond? What is your water temperature? How much sun does it get? Do you add any chemicals to your pond? Photos help.

 

[j.w]

@Stevechi
Maybe lack of fertilizer (fish poo)? I've heard of people taking them out and putting them in a container to soak w/fertilizer. If the water lettuce plants are few in number or are small, you can just take them out of their pond gently and put them temporarily in liquid fertilizer like Miracle Grow. Only leave them in the liquid fertilizer container for a few hours at a time, to avoid overdosing the plants.

Or maybe the cause is too much scorching sun?