Could be alot of things,however i live in texas and it gets sweltering hot!The tomatoes i have
growing are doing very well.A few possibilities are that the pots may be too small and or lack of nitrogen.Sunlight is important,but i have allso heard that moonlight is just as important to nightshades.Naturally plants never move from the very spot they are born and who really knows what effect putting them in pots,or moving them to different locations really has.I imagine it is a shock to thier systems to live such an unnatural life.Most plants i have grown in pots require alot of maintenance mostly becouse i do not use fertilizers,only add new dirt or composts.The soil should be spongy,moist,and dark.overwatering however can couse roots to rot and disease to take hold.