Various species of stink bug have been known to attack cannabis plants. They lay distinctive patches of white eggs, which hatch into small beetle-like insects and eventually grow into stink bugs. I've never personally encountered this insect myself, but they attack many marijuana plants both indoors and outside so I'm gathering pictures in information to
Plant Problems Symptoms: Pink or purple on leaves
Cannabis leaf edges and tips turning yellow? Copper deficiency can cause dark, shiny leaves with purple or blue undertones. Learn how to spot and treat it!
Phosphorus deficiencies cause dark splotches on leaves and can appear at the bottom of the plant on some of the oldest leaves. Learn to spot & fix the issue.
Problem: A cannabis sulfur deficiency causes yellowing of leaves, usually starting with the newer leaves. At first it may look like a nitrogen deficiency.
Problem: A cannabis molybdenum deficiency causes leaves to turn yellow. The leaves may also display a unique orange, red or pink color around the edges.