You probably answered your own question. You don't use CO2, but you increased the lighting on the tank. The more light you have the more important CO2 becomes. And, the more light and CO2 you have, the more important the nitrates, phosphates and traces become.

But, back to the pruning question. hygrophila varieties are stem plants, so you can always prune them by cutting off the top and replanting the top, and/or by leaving the trimmed stubs in the tank to sprout new leaves. It isn't a delicate plant at all, even though a very few of them are not as easy to grow as others are.