Do Vals go through growth cycles?

[Mr. Breeze]

I planted Vals (Valisneria - Italian) about three months ago. They took off and shot runners everywhere. Over the last 30 days, they have wilted a little bit and lost their color in places. Some brown leafs tend to separate and float to the top. I pick out 2-3 a day.

Is the plant going through a dormant phase or am I now lacking adequate nutrients? This is a heavily planted tank. See photo.

Thanks,

Mr. Breeze