I just finished typing you and had a big ass answer for you but damn Firefox randomly closed and fucked it up.
I'll attempt to type it over just cause I'm a lil high still.
To acquire a computer fan you can get it from eBay, just do a search for it. Really cheap sometimes less than a dollar if your lucky.
Computer stores have them, and you can even get them from older computers you don't use or something like that. There are usually 2-3 computer fans in one computer. You really only need two but I have three. Two for intake and one for exhaust threw Activated Carbon.
You can use them to point at your plants cause a good breeze is always welcomed when growing Mary, and it allows for the plants to get a nice stem going for heavier buds.
Next step above that is getting a home made Co2 bottle from yeast and shit, look it up on here, some great examples. That with the circulation they will love it.
Not sure your full set-up but your roots are super nice.
And your yellow leaves could be that your plant is getting burned from using too much nutes.
Keep me updated I'm watchin