"Compost from a local store" - do you mean a potting mix? I ask because frequently they contain fertilizer which you have then supplemented with additional fertilizer.
However, my initial very broad guess leans to over watering. You say you soak them every morning - do you check to see if they need water? Tomatoes don't want their feet in constantly wet soil. Ideally you should only water them when the soil has a l m o s t dried out. Easy to check using your finger to a depth of a couple of inches...often the soil at the top of a container looks (or is) dry because of exposure to sun, air and air movement while the soil beneath is not.
As a start I would hold off watering until you are sure the plant needs it. Others will likely have more and better answers.
