Do you think that there's a high likelihood that I have too much light? I'm getting stunting in my R. rotundifolia of all things.
Intuitively only, I think you probably have high light, but I don't see that stunting any plants. Any stunting would be from a shortage of a nutrient, probably CO2. With high light you do need a lot of dissolved CO2 in the water to enable the plants to grow as fast as the light is driving them to grow.