It will be a nutrient effect.One strange thing, the floating plants are growing really well in the 10L and are a good size but seem to be getting smaller and smaller in the 37L?
The new leaves look a healthy colour, but the older leaves are definitely struggling. Because it is the older leaves it is a mobile nutrient, and nitrogen (N) and potassium (K) are the most likely ones to be deficient.The big ones are a little bigger than when I first bought them in the pot. The small ones are considerably smaller.
Much bigger (<"and bronzed?">) in the trug would be my guess, so it might be a light intensity issue as well. These plants grow naturally under tropical sun-light, which is really intense.When I get a minute I’ll take a picture of some that are outside in a trug.
Mine on the pond look the same. They are beginning to suffer from cold and/or lack of light.but these are the ones outside