Small dark markings on leaves

[Ganja87]

Hi guys 

 

Can anyone tell me what this faint dark marking is on these leaves? (the closest 2 leaves)

Could it be a possible magnesium deficiency? 

 

 

Peace

Ganja

[Matanuska Thunder]

you are over-thinking it

most probably the spots are from water/nute burn 

[Sir PsychoHashy]

Could be, but it's not a certainty.  Looks like a little bit of nute burn on the tips possibly as well.  Having said that, I don't see anything going on to get into a panic over at this stage.  If it spreads up the plant, then you can panic

 

If you are worried, add some cal/mag to your nutrients as this isn't a bad idea as a preventative in coco.  Also make sure your nutrient PH is okay, and maybe back of your strength and then work it back up over time until your plant is at it's happiest.