You should help your hens stop laying soft shelled eggs for two very important reasons. The most important reason is for the hen's health. The second reason is your flock will soon learn to eat eggs if there are soft shelled eggs around. Once a flock starts to eat eggs, it is very difficult to get them to stop. They will quickly learn to break into eggs with hard shells.
Sometimes stress or molting can cause soft shelled eggs. Many birds lay soft shelled eggs not because they lack calcium but because they can not take up the calcium. Most commercial layer feeds have enough calcium. If you supplement a commercial layer feed with crushed oyster shell your birds should be getting enough calcium.
Chickens need vitamin D (actually vitamin D3) to take up and use calcium. Stress and some diseases make hens unable to process vitamin D. Vitamin D is in many feed ingredients. Whole grain wheat was the traditional source of vitamin D for chickens. You can also supplement your flock's diet with wheat germ oil that is fortified with vitamins A, D, and E. Give bantams about 1/4 teaspoon and 1/2 teaspoon to large fowl.Here is a list of things you can do to prevent or stop soft shelled eggs.