You'll have to start very soon. Once you see symptoms their levels are too low and could progress into worse...inability to walk/hop/climb, open jaws, seizures, weak bones...to Metabolic Bone Disease.

I would pick up some liquid supplement and the powder. Start with a liquid soak today and daily until the twitching stops and he can move better. Then start the powdered supplements as the usual schedule ... Calcium/D3 every other day and MVI once a week. After the soaks start with the MVI. Be sure the calcium has vitamin D3 in it and be sure it is phosphorus-free. Vitamin D3 is needed for proper calcium absorption.