Help! Why are my leaves starting to curl and brown on the tips

[danopano]

So for the past few weeks the tips of the leave shave started to turn brown and curl and a little. What can be the cause of this? And what is the best solution.

My plants are all completely outdoors.
Cheers!

 

[Antics]

There are a few things that cause symptoms similar to what we're seeing here, could you give us some more information about your grow by visiting the following link, and filling in all the information?

How to Ask for Grow Support

 

[BuddroGreen]

Nute burn or

Potassium Deficiency...give more (K) N-P-K