Plant problem HELP

Okay I just got done transplanting it but before I did this is what it look like I’m doing 18/6 light schedule haven’t fed yet I’m on day 21 right now this is how they look what is that

You have a slight Mg deficiency

Capn-Crunch said:

You have a slight Mg deficiency

Click to expand...

I’m getting different answer one said potassium

Capn-Crunch said:

You have a slight Mg deficiency

Click to expand...

could it be this look like nutrient burn or sum plant look kinda like this running along the edges of my leaf