Why is this avocado leaf curling and turning grey?

Question

I have 3 avocado plants in a small pot. They are about 2 months old. One leaf shows a grey discoloration with curling around the tip.

What is causing this and how do I stop it from progressing?

Answer 1

Leaf tip burn is caused by accumulation of fertiliser salts at the leaf tip which then kills the tip and the edges brown and die back. The problem is caused by excess fertiliser salts at the surface, and can be remediated by watering deeply to wash the salts out.

https://garden.org/nga/searchqa/answer/23491