Tiny Brown Spots

Hey, plants been growing for 3 weeks now, it is Afghan Kush Ryder and i have it on a 20/4 light schedule as recommended. I was wondering what you guys think about the size if it is the size it should be after 3 weeks. I also noticed today that there are tiny brown spots that are comming up on most of the leaves, what do you think is wrong?
Thanks for the help pics below.

I am assuming it is an auto strain with budz appearing in 3 weeks and on 24/0. I think you may have a couple of issues here. First nute burn, what is in the medium you have her in? what is the PH? What nutes and how often are you feeding? The little spots, not to sure but I would check and double check for critters. I suggest doing an RIU and google search on these issues to gain better knowledge and good info. Best of luck!

It is on the 20/4 light schedule and i am actually not using any nutes at the moment and i only water when it is dry.

I'ma go with the popular Ca-Mg def issue. You're plant doesn't look hungry rather the opposite.

Ok, im going to try foliar feeding with a mixture of ebson salt to cure the mg problem and dolomite lime to fix the ca problem? Does this sound right?