Nute Brun ? Disease? Help please

[GowerX616]

What do you guys think this is ? Any help would be appreciated. They just started week 5. This is the main plant effected the other has almost no signs of this red/brown color. I suspect nute burn but this is my first grow an want a second opinion. I did flush 2 days ago but the leaves are still wilted to an extent.

 

[SofaKingHigh]

We need some more information to help you out. What are you growing in? What are you using for nutrients? Temps/humidity in grow area, what light are you running and how far away? Also a full plant pic would help.