The chances of the dropper size being incorrect are remote. The precision of the hole size actually has very little to do with the size of the drop......it is the spherical shape of the tip that allows the drop to form through surface tension and then fall off the tip by gravity. The supplier of those tips doesn't make any other size and they are ordered in large quantities.
How do you know the CH test was incorrect?
What was the result of the CH test?
We'll help you get it figured out but, I promise, it will not be the dropper tip.
Post back and give us a bit more info, I think it can be solved pretty easily.