Yellow leaves with green veins, interveinal chlorosis deficiency of probably magnesium, also the purple color is also a 2nd sign of same. Green to yellow to brown is the progression leading to dead...
50* is a magic number in Mother Natures realm. At 50* all night temperature a baby chick can survive without heat or mom. At 50* water temperature we stop feeding fish as they can not digest what they eat and it can kill them. At 50* soil temps plants stall in their growth patterns and we stop watering them. They will resume growth as the night temps maintain 60*.
Too cool, too much rain, they simply cannot uptake the nutrients they need.
