It's not light burn or heat issues.

Looks like moisture retention or possible transplant shock. Make sure the soil is near-dry before watering or feeding. Cannabis prefers a wet-dry cycle. When was their last transplant?

Full-strength CalMag is unnecessary during the growth stage, and it will cause problems when overused.

Did you top her already, or is that just how it's growing? What are the overnight (low) temps?