Cannabis is in reality just a weed and is indigenous almost everywhere on the planet...growing quite healthy in outdoor gardens where the grower cannot control wind. The issues you are having is not in all likelihood due to the fan. You have a nutrient problem...could be deficiency, could be excess, could be ph, could be this, or could be that. What I am getting at is that this is your grow...you know what you put in your medium mix. Something is not right...try this web site
http://www.growweedeasy.com/cannabis-symptoms-pictures
We can only give you our 'opinions'...Knowing what you did is causing a problem...get some cultivation knowledge and make your own diagnosis and fix it. You will get a more accomplished feeling correcting it yourself then taking our word for it. We do not know specifically what caused the issue...we can give you general advice but at the end of the day it is your grow and only you can determine what is best for it.
Good Luck and Great Growing