No diary = no information with which to help you.
Looks very dry. The yellow in the oldest leaves is probably nothing to concern yourself with unless it also shows up on the newer growth (not seeing that yet). Don't know what you're feeding, don't know your pH, ... really, there's no information. Seriously, dude - if you had bad pain in your stomach for a week, would you take a picture of your belly and send it to the doctor asking what was wrong? That's essentially what you're doing here... Start a diary - even if you can only reconstruct one or two weeks - and ask your question again.
Good luck...