Going to disagree with my growmies here.... your pH is fine... anything between 5.5 and 6.2 is where you need to be and you're there. And I don't think this is a result of anything dropping on your leaves and burning under the lights... my opinion is that you need to add some calmag from the get-go, especially if you're using Fox Farm (I used Fox Farm when I grew in soil and absolutely hated it as I always ended up with a nitrogen toxicity from their Grow Big resulting in calcium deficiency)... I would suggest you knock down the Grow Big to 1/2 tsp and add 1tsp calmag because what I'm seeing is a calcium deficiency... and your EC is fairly high for this stage of her life...
Good luck