What is this?

I am just wondering is this Mg or Ca? Or could this be toxic salt buildup?

looke like you may splashed som mix on the leaves or its nuts. burn. need more info in order to help

More information? Do you mean strain, nutrient line, soil?

I flushed Wednesday then the next day I was doing my daily check in my room and I noticed this. I just used regular RO
water, but didn't add no nutrients. So I thought it was a Ca or Mg deficiency so I added General Organics CaMg+ (5ml/1gal) RO water and watered it with that. Then let drain for 20 minutes and took pH it was 6.2.

Also I had found some thrips so I used FoxFarm Don't Bug Me spray and sprayed where they were located, but I didn't spray those leaves. Maybe some mist found it's way to them? It just seems to uniform for that though.

Also the tips of some other fan leaves and I mean just the tip are that color also. Maybe two other fan leaves tips only have this color so it would be nutrient burn right? Or magnesium? These are new strains I am trying. Sour Grape.

I meant this is a new strain I am trying.