I have a litter of puppies and two from the litter (all yellow litter) have black dots on them about the size of a dime, one has it on top of the head, the other on the chest. What causes this as ive never seen it before.
Thank you.

While it is not common, it is not unusual to have something like that happen.
Here is a good link to other pictures of 'mis-marked' purebred Labs. Sometimes the 'dots' get smaller, sometimes they do not. The good news is that the markings in no way detract from being great hunters, companions or otherwise all round great dogs.

I've understood the dots as misplaced pigmentation as they are not quite like a Splashed mismark, just a spot. I have run into two pups in my own breeding program that have had this, both I placed in great pet homes. I have also seen one girl that another breeder was showing that had a small black spot on her hip and it never slowed her down from doing very well.