need help identifying problem (first grow)

It does look like a slight N toxicity, the brown tips are from to many nutrient. I noticed you don't feed with every water which is good because less build up in the soil. Make sure you always get a decent amount of runoff when you do water. I would give her a good flush. Make sure your on a bloom formula, but you may need to start flushing in the next few weeks as she doesn't look that far off.