First grow, need some advice.

I currently am in my first grow. I have four plants coming up, three under two "grow" lights from Wal-Mart (Lights that claim to be plant growing specific) and one under it's own bulb. The plant under it's own bulb is growing much faster than the other three (which I attribute to the different lighting it has) while the other three grow nice and steady but at a slower rate.
The three under the two bar lights have started to get yellow spots on the leaves at the bottom and the shoots seem to have a little red in them, while the bigger plant has more of a cancerous (more like blotching than spotting) spotting also on the lower leaves. In this set up I also have a small fan at the top of the closet that blows 24/7. I had them on a 24 hour light cycle when they where small, but when I transferred them to their three gallon buckets, I put them on a 12/12 lighting system.
I have been growing them now for about three months and although they get bigger they do seem to be a bit stunted.

So my questions are as follows...

-How to cure the red shoots and yellow spotting
-How to cure the blotching on the leaves
-Should I be running the fan 24/7
-Should I be on 12/12 lighting
-How do I know it's the right time to flower them and how long should that process be
-How long should they grow before it is time to flower, after almost three months they are about a foot each, should they be bigger at this point
-How much yield can I expect per plant

I appreciate any and all help I can get, I didn't even expect to get this far, but now that they are about a foot tall I want to see them come to flowering.

Thanks!

so if you want help on the plant trouble you need to post pics, otherwise it's just shooting in the dark. also tell us about the medium and the food they've been getting.
the fan is better to run 24/7 yes, for proper air exchange and to avoid mold problems due to moisture.
12/12 is a matter of choice. once you turn, you can't go back. well, you can, but not on your first grow. after you switch them they will start to flower in a couple of weeks and finish in a couple of months. but they will stop growing at some point. so you wanna grow them as much as you can/want on 18/6 for example, and then switch to 12/12.

the size of your plants is determined by many factors, including light, but 1 foot in 3 months is abnormally poor, it means they have serious problems with the environment, genetics, or both. 3 months is too long to get 1 foot. you should read some about growing to find out why this is the situation. from three plants of 1 foot each, if you solve all the problems right now and give them a good growing environment, you can expect maybe 2 oz. but again only if you give them proper medium, nutrition, light (HID), temperature and a pest free environemnt.