White spots on the teeth can mean Lack of any of the following, Calcium, Magnesium,vitamin D, and phosphorus
Take note, all of the above are needed in to absorb ANY calcium. the a lack in just one means your calcium absorption is Extremely redused.
Likely y'all are all getting enough Calcium, so the more likely cause is Magnesium,D,Phosphorus all in that order.
Vitamin D is found in milk (Synethic), cheese, whole eggs, liver, salmon, and. The skin can synthesize vitamin D if exposed to enough sunlight on a regular basis. Also from supplements.
Most leafy greens contain a good deal of Magnesium (if soil is rich). Also most nuts contain Some Magnesium.
Phosphorus is found in milk, grains, lean meats.