The delay in the closure of the anterior fontanelle, the soft spot on her head could be a normal variation since she is doing well on all accounts. The common causes for the delay include hydrocephalus (large head with collection of fluid in the brain), hypothyroidism (poor function of thyroid gland) or rickets (abnormal bone development due to a variety of causes). In all these situations the baby generally has a delay in her development and other tell tale evidences of the disease on clinical evaluation. The soft spot may close in another 3 months most probably. There is no harm in continuing with calcium.