Please help a first time grower. Dark brown edges on leaves!! Thank you in advance!

I've already done tons of research and couldn't find a correct diagnoses for the problem I'm having.

I forgot the name of the strain. It was a free sample I got when I bought my auto flower white widows. The white widows I've already harvested at 12 weeks without a problem. But this one start showing problem at week 10. Leave color appears pale overall and the lower and middle leaves start showing yellow patches. Then at week 12 the some of the upper leaves start showing black/brown at the edges and tips and the lower leaves look paler than the upper ones. I'm using 50/50 coco and soil. water ph is around 6-6.5. I'm using worm casting and bottle nutes. My parrot power flower is showing that the nutes level is on the lower end.

Thanks for reading this and I look forward to your suggestions!!

could be a potassium deficiency

go to www.growweedeasy.com and look it up lots of info and pics

Its nute burn because the medium is unsuitable for marijuana. Use quality coco next time so you control the nutrient level and get much better growth

Potassium and/or magnesium deficiency.

Yawn. Typical plant with some blemishes.

You're green.... you're good.

Or try to correct the "problem", make sure to take pics as you go.

here, this has helped me, hopefully it helps you as well as anyone else who is interested.