If you are talking about the brownish color near the top , just sticking out the pot then I would say no.
My first dwc I had something similar, what I put it down to was it was because I didn't top fill those bubblers at any point, and the water level wasn't usually filled up much past the beginning of the net pot.
So I put it down to them just discoloring because they them self weren't getting much water, when I dug the roots out some where as thicker than pen's, which I thought was great , until I read it was a bad thing that they do apparently when they are trying to find water.
As others have said root's look fine otherwise.