Dark spots on one of my plants :(

[BigBud09]

I have dark spots on one of my plants?? the bottom leaves seem alright but there's a couple on top that have developed dark spots on them, any1 know what sort of deficiency this is? i have another 2 plants that have cal/mag deficiency i think, check the pics out ppz let us know thanks

 

[Green81]

thrips and or mites,, get them sprayed pronto

 

[whiteflower420]

dirt, or water,

 

[BigBud09]

I don't think it's thrips or mites I have checked underneath the leafs there are no eggs, i have about 10-12 ladybirds in my grow room to help with any pest's or insects, my room is clean apart from the ladybirds

 

[Green81]

possibly some sort of micro nutrient defeciency, magnesium?

 

[BigBud09]

I bought some CalMag the other day ive been giving them 5ml's of calmag to every gallon of water lets hope it solves the problem i think it will take a while for the calmag to take affect