3 different leaf issues

So I've noticed that the leaves on most of my plants are displaying some sort of issue. I think a lot of it is nute burn and subsequently toxicity of certain nutes but I am far from a professional so I wanted to get this communities opinions, please take a look and tell me what you think.
So I found these marking on every affected plant, it only seems to be on the lower smaller leaves and the higher bigger leaves seem untouched
I have only found this type of marking on 2 of the plants, but it's only on a couple of the leaves rather than a lot of them and it's only on the big leaves at the top of the cola.

And as for this issue I have only found it on 1 plant but over half the leaves on the top are like this. Any help would be appreciated

More info is needed for someone to help you here.
Plant age? medium? top or bottom leaves the issue?

goofy81 said:

More info is needed for someone to help you here.
Plant age? medium? top or bottom leaves the issue?

Click to expand...

The plants are approaching 3 months in veg. Growing in canna coco coir. Picture 1, the dry crumbley leaves only appear at the bottom. Picture 2, the brown/red spots only appear on a couple leaves at the top, on only 2 of the 6 plants. Picture 3, the yellow edges are on almost every leaf at the top, only on 1 of the plants. I am almost certain it is due to over feeding as I was feeding 5ml per 2L of water of mills base nutrients, which is over double the recommended dose, because I read the instructions wrong, and I have only just switched over to that brand. I was just double checking it wasn't a disease/fungus.