When Should I Start Supplementing My Baby with Calcium and Cod Liver Oil?

My child is almost 90 days old and has been experiencing restless sleep lately. He struggles intensely at night, often wakes up startled, crying, and has severe night disturbances. I’m worried about a possible calcium deficiency. Should I supplement with calcium and cod liver oil? How should I administer the cod liver oil? Thank you very much for your help!!
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