Sounds like a bow problem to me. Have you paper tuned your bow? And if so I'd check to make sure nothing has moved accidentally. The fact is you repeated the problem 4 times and with different arrows hitting different each time. In my mind that should rule out the arrows and your technique. Only thing left is the bow. I'd bet money it needs paper tuned. I like to mark everything (rest, sights, peep and limbs)with a sharpie or paint stick afterwards so that if something does move accidentally you can spot it right away.
Also I've seen bow dealers "tune" the bow at the shop with a laser, in my experience that's not always the best method. Each bow is different and shoots different so just because everything is perfectly in line doesn't mean your bow is tuned. Oh, and check to make sure your fletching isn't hitting your rest or anything as it goes by your riser.