Potassium deficiency?

I'm thinking it's a potassium deficiency because it's yellowing from the outside in and the tips of the leaves are slightly curling downward. I'd just like to get a few more eyes on it to be sure. Thanks guys.

EDIT: Here's a pic from a neighboring plant:

Unfortunatly the picture doesn't reveal it clearly. You should take another picture of it where the macro is focused on the leaves not the stones. Still this picture shows only the beginning of a defiency so it cannot be clearly classified yet. Could be several things.

I did, I uploaded another. Sorry, it was taken with a phone lol.

Yeah the second picture is a lot better! I suggest you wait and see how it develops. It's to early to tell exactly what defiency this is.

Here's an example of pottassium defiency:

Okay, thanks.