Pleanty of water and some plant feed or tomato feed, As They grow bigger they use a lot of water and more of the goodness in the soil/compost. If there in the sun a lot you will have to water them most evenings. The leaves start to flop mainly because of lack of water and/or food. If they have been moved from a different location,maybe they are getting more wind or more sun on them that can cause them to flop as the change of enviroment. If this is the case they may well take a few days or so to pick up again and get used to the new enviroment.