What is this? Nute burn?

After topping theese clones 3 days ago the top of the stem turned black...What is this? Are they dying? Never seen before..

Looks red to me. You really need to give up as many details of your grow as possible.

Some plants do this when you cut them, it just died back a bit from shock of being cut, should be completely fine tho..

codemonkey said:

Some plants do this when you cut them, it just died back a bit from shock of being cut, should be completely fine tho..

Click to expand...

This is the thickest stem I have cut for a clone ever...Looks like Its ok. Guess Its shocked after beeing topped off