Lotus lily question

I  have three lotus lilies that provide a nice variety of color to my
75-gallon tank. The plant that has been the most vigorous in its growth
started out with many leaves and has continually produced many floating
leaves. However, the submersed part of the plant seems to be diminishing
while it continues to send up stalks with floating leaves. (At present there
are five leaves on the water surface.) Are the floating leaves responsible
for the submersed part of the plant diminishing? Do I have to choose between
one or the other?
The tank, by the way, has laterite in the substrate, DIY CO2, daily doses of
Dupla drops and 160 watts of Triton tubes. Everything else in the tank is
going gangbusters.