2nd grow and I noticed yellow spots on the plant. How to fix?

[DR.PNW]

Skydiver is on the right track.
The classic Ca Mg issues, many many, many threads on Ca Mg importance in cannabis cultivation on this site. Especially when growing in coco…
Check this thread for info on Coco:

COCO: Demystifying the medium

For all those out there who are interested or have chosen to grow in coco and have yet to learn the intricacies of it: I have a long history and deep understanding of coco and would be happy to impart and enlighten those who have questions, concerns, facts, discussions, etc. Coco is so often used improperly. It is truly an incredible medium that stands in its own category, and thus requires specific attention and actions. If other threads have not been able to answer your coco-related inquiri…

For bugs: Get yourself a 30-40x lighted loup/microscope to keep your eyes open for bugs.