leaves turning brown & curling upward

[Smarty]

Calling all plant Doctors I’m looking for some opinions. My plants are in an aeroponic grow. PH is 5.8, I feed with mills which I have used the past 4 grows with no issue. Leaf tips curling up and turning brown. I have included 2 photos. Any Ideas?

 

[D.A.A.S.69]

Root bound for one thing.

 

[Smarty]

How can they be root bound?

 

[UrbZ]

Once a plants leaves reach the edge of the container the roots will have done the same. Once that occurs its not long til rootbounding happens. A week or two of growth. It is basically suffocating your roots in the little pot.