I’ve been looking into vitamin A/C/D supplements as DS is on 3 meals a day now and will probably be dropping below 500ml of formula soon.
Reading up on this, it suddenly occurred to me that when DS was a newborn, he probably wasn’t on 500ml of formula per day to begin with as that sounds like quite a lot - but I never gave him any vitamin supplements!
I think I wrongly assumed that you didn’t need them with formula, but of course that’s incorrect if they’re having less than 500ml. Could this have done any damage to DS? I feel so stupid! 
Also, how do you administer the A/C/D vitamins once they need them - can you get drops? I do have some vitamin D drops but not A/C - can you get them as an all in one?