They are exactly the same bullet with the exception of the lubalox coating. It's not MOLLY.
All of the deer were lung shots, but only 1 has dropped on the spot....
You can not expect a bullet to drop an animal on the spot unless you break the spine or shoot it in the brain (not necessarily the head). All deer will react differently to being hit with a bullet. I have had only one animal drop where it stood and that was a mulie doe inside of 20 yards and I shot her through the front of her neck and blew it out the back with a 7mm Rem mag.
A 50 yard recovery is pretty dang good. Be very happy with your results.