Deficiencies? Brown spots, yellowing and purple stems

Your at the stage where those fabric planters are getting full of roots which make the water start channeling through your dirt like a river flows. Path to least resistance. Let the planter sit in it runoff water for a wwhileto soak some water back into the planter. When you leave dry spots in your root zone it creates these spots, usually mid to near the top of the plant. Also check your runoff waters ph and ec levels, make sure everything is good. Cheers