dude im pretty new to the indoor thing as well but, those seedlings look like they are struggling for light. if you gotta go cost effective, i'd put some cfls, on those things asap, and within a 6" or so, also i'd try to get a hold of some bigger pots or at least use the whole styrofoam cup for now, when you replant, i'd also bury them a little deeper to counteract some of that stretching