Too much light?! You can never have too much light bro. Just dont put those big lights near your plants because they get very hot. Put a hot ass light close to you for a whole day and see how it feels, lol. So pay attention to your temps. High temps stress some strains of cannabis out too much. A good temp range, depending on your strain is anywhere from 70-85*F. Depending on the strain some like it hotter and some like it cooler. I had a strain i found in hawaii last summer thriving in 90*F temps with somewhat high humidity. Thats because it was acclimated to those conditions already.

As far as the spider mites, shit man, i have no idea.