Blue Rhino Positronics

I noticed brown spots on the lower foliage and some yellowing around the tips of the leaves. I didn't heavily amend this soil. I went ahead and did a half strength batch of Advanced Nutrients-Grow, Micro, Bloom to see if that would help. She still growing vigorously and has super tight inter-nodal stacking. I'll be transplanting her to a bigger pot but I want to cure this deficiency first as to not add extra stress.