As we know, people blink for the purpose of the breath exchange for the air which will keep the eyes moisture. You could find that we like to blink for the prevention of the dust and bad things too. If you blink slower than before, you'd better go to see the doctor and have the check on the eyes.
All right, from what you said, I can see that there is something wrong with your eyelids, because as you can see, generally speaking, the speed of blinking of both of our eyes are identical with each other. If one of them is abnormal, then there must be some reason, I mean, maybe the muscle of your eyelid has got some problem, perhaps this is due to a lack of vitamins and something wrong with your nervous system. Sometimes a lack of vitamins and minerals might cause such problem, and you should take an eye exam before taking any further actions.