i don't think its a sign of defiency, your plants look decently healthy. Because theyr'e outdoors, even though its not getting cold yet, temps are starting to drop considerably at night. These are just at the growth tips as well, no where else on the plant. You'll also notice that the leaves lose this purple coloring as they growth outwards from each node....they start purple and turn green. I've seen it happen many times with indoor and outdoor plants, and it always comes with the fall/winter temperature dip.

Some plants are very finicky when it comes to temperature and humidity. Depending on your genetics, your probably growing a strain originating from SE Asia or the middle east. A 10 degree drop in temperature is a huge deal to a plant that's might be genetically programed to flourish in hot weather. These pain in the ass strains always seem to be the dank though..........