With only 3 plants you probally won't have a huge odor problem, all depending on strain of course some are smellier then others. I got some ona blocks for my small grow of 4 plants. There was defintaly a jungle smell in my room and so far 1 block has done a good job of getting rid of it, I also got 3 more for when they start smelling more. Their only like 10 bucks each and last a while. You can find them at any hydro store.
Once you get some more lights for your ladies I would get a fan blowing on them as this will help strenghten the stems and also give them good air circulation.
Good luck with the grow.
Oh as for that splotch I can't really tell what it is, but its nothing to be to worried about just looks like a light burn. I would just leave it, as taking of leafs from that young of a plant would be a bad idea.