Rickets is due to a lack of vitamin D.  Congenital nutritional rickets present tremor, secondary hyperparathyroidism, craniotabes, low vitamin D serum levels, hypocalcaemia, and weak muscle tone. 
2003 Journal of Orthomolecular Medicine   www.orthomed.org
Vitamin D is needed for stomach to absorb calcium from food.  Vitamin D is made by skin from the sun's ultraviolet light.  Dark skinned people are less able to make vitamin D than light skinned people and should be careful when choosing sunscreens.  Some dairies have added vitamin D to milk.  Vitamin D is also found in cod and halibut liver oil and was used by Europeans during WW1.  Calcium is stored in bones.  When calcium is insufficient to regulate the heartbeat, the kidneys will release a hormone to trigger
a calcium release from the bones.  Insufficient calcium and/or vitamin D may create rickets.  www.darshaksanghavi.com Health Science editorial 11/7/05 www.bostonglobe.com
Vitamin D is made by body via daily exposure to direct sunlight.
Wallach, Joel - 9/23/2016 - Recommends Vitamin D3 (especially via sunlight)
Wallach's Concern Trace mineral tablets or powder available at www.traceminerals.com