Leaves turning yellow, unusual spots

A few leaves on my plant have been turning yellow for the past couple weeks and some have brown spots. There is some weird spots on some other leaves too. I water it every 3-4 days. It is around week 4 of flower. Can someone please tell me if it's going to be alright. Thanks.

I have worked out that you do not use a ph tester, that would be the first place to start.
Whats the npk of your nutes too?

Your leaves will turn yellow late on in flowering but i dont know thats going on now.