HELP! Help Diagnosing Leaves

[guilty]

I'm back again! 1 out of 4 of my plants has developed these spots and some of the leaves are lighter in color on 2 out of 4. I'll attach a picture of all plants. I went on the troubleshooter here, but I'm having a hard time distinguishing between light burn or nutrient (calcium or magnesium deficiency?) This is in coco under a 315 LEC. 5 gallon smart pots. General Hydroponics nutrients.

Here is my most recent feeding schedule:

Feb 24 - 3 gallons - week 5 schedule + 1/2 tsp/gal of cali magic + 1 tsp/gal hydrogard - 2.5ml PH down in 3 gallon - PH 6.3

Feb 26 - 3 gallons - week 6 + 1/2 tsp/gal of cali magic + 1 tsp/gal hydrogard - 8ml PH down in 3 gallons - PH 5.6

Feb 29 - 3 gallons - week 6 + 1/2 tsp/gal of cali magic + 1 tsp/gal hydrogard - 4 ml PH down - PH 6.3

Mar 4 - 3 gallons - week 7 + 1/2 tsp/gal of cali magic + 1 tsp/gal hydrogard - 6 ml PH down - PH 5.5

Mar 6 - 3 gallons - week 7 + 1/2 tsp/gal of cali magic + 1 tsp/gal hydrogard - 4 ml PH down - PH 6.1

Mar 9 - 3 gallons - week 7 + 1/2 tsp/gal of cali magic + 1 tsp/gal hydrogard - 4.5ml PH down - PH 6.1

Any pointers or help diagnosing would be greatly appreciated.