Should I worry?

mildew spreads fast. generally forms circular colonies to start.. so if it is staying the same over time, more likely something dripped on it and just seeing dried up solutes. If it is mildew -- take a cloth with some h2o2 (hydrogen peroxide) and wipe it off. Careful, it will bleach the cloth. Dilute to 1/5th to 1/10th a normal 3% stregth and it won't hurt your plants. Neem oil spray can deter microbial growth. Other fungicides are out there, but will cause some sort of damage to plants, often... like potassium bicarbonate or a copper soap. I'd only use those on a more mature plant that can handle losing a leaf or two. sodium bicarbonate (baking soda) is also an option. Google "Cornell Formula" .. involves baking soda, some soft soap etc etc. ==> homemade foliar spray... Deformity -- if not caused by a drip and some stuff drying up on it... could just be normal. early sets of leaves are potentially blemished or ugly... but, they will be beatiful in a few nodes of growth, no worries... so, need to observe and eliminate possiblities before choosing course of action. Some of the fungicide related stuff can be used as a preventative measure. Once a plant is infected with WPM, it's very difficult to get rid of it... constant maintenance to keep it in check -- spraying with a fungicide and removing leaves etc etc... keep it minimal and you'll still get a harvest you are willing to smoke.

Could you get a closer picture. It almost looks like you could of spilled some nutrients or PH adjuster on it and the white is the dried out salts. Mother earth mix does not contain any nutrients and I see you are only feeding GH micro. which is missing potassium. I have never see a lack of P cause that though. Also check PH of your runoff. It could be out of wack which can cause all sorts of things. Happy Growing.