Vegetables are the fruiting structure of the plant and if not completely pollenated, then the fruits will abort shortly after they start to expand. Poor pollination can be caused by several factors, limited bee visits, poor weather, no male pollen available. The other reason is often a temporary lack of calcium at the blossom end of the fruit which will also cause rotting. Usually the calcium problem goes away after the first few fruits form as the root system naturally is expanding.
