Hi I probably should sit back and learn as I've limited exposure to stamps.
When it comes to dots and differences in one stamp to another I'm not sure what's acceptable as normal plate wear, polishing or improper transfer, etc.
I did notice when comparing your first two stamps some differences that I circled in blue.
I had noticed a while back that part of the detail in the water is shaped like a duck and some have a red dot in the body part and some don't, circled in green.
The third picture is mine where the duck appears different and hasn't been shot.
Are these differences all normal and acceptable and can be explained?