First Grow Ever. The Girls Need Some Help!!

-Problem: Discolored leaves appearing after a healthy veg and early flower
-Medium/grow method: Coco Coir/ perlite 70/30%
-Feed and supplements used: GH Flora Trio. Currently 2.5ml calmag// 2.5ml micro// 0.75ml grow//2.5ml bloom per gallon (After research this seems a bit low... opinions?)
-Water source: Tap water ph to 5.5-6
-Strain and age: Day 50 Hindu Kushx Bloody skunk (SoFem Seeds)
-Climate: Temps hovering at 75F and Humidity around 65
- Light used: 24/0 SF2000 at 18-20 inches
-Additional info: This just popped up over the past few days. I'm thinking its a calmag issue. My plan is to increasing the calmag but since this is my first grow, I'd like to hear some opinions. The leaves have started turning a brighter green/yellow and these brown spots have started appearing on quite a few leaves... probably around 20% of leaves.

I don't know anything about coco and led's but you are a little light on the feed. I use a lot of Lucas formula with GH and 5 ml micro/10ml bloom per gallon has been proven safe and sufficient for years. We have a lot of threads here with led and coco problems, maybe you could glean something from them.