Phosphorus deficiency (P)
Older leaves will show brown discoloration along their edges, frequently accompanied by deformation. Leaf blades, originally bright green, will turn yellow, followed by purplish-red discoloration of leaf veins.
Treatment: Soil analysis will help to determine whether an application of phosphorous is advisable. If the analysis shows a generally low phosphorous content of the soil it is advisable to apply phosphorous annually.