I think it is good that you have gone to the trouble of obtaining density measures of your weights. But could you please let us know how you did this - in other words, what "kitchen" method did you use. I ask because this has often been discussed amongst members of the PCC and, as yet, I have not heard of an agreed "kitchen" method that could be easily used, with a fair degree of accuracy, by other folk.
For my own density measures, which I made using a setup similar to that outlined by John Hawley, I found a variety of discrepancies, not only between results of other people, but also between my own repeated measures of the same weight!
One aspect that could well be important is the temperature of the water. There is a table of adjustment factors that are used by "professionals". When I tested this with the same item, with all other conditions the same, I did get some differing results in the decimal places.
Another factor that is suggested by some folk, is the "purity" of the water. However, I have found no differences when using "pure" water (as sold for use in batteries) and "hard" tap (faucet) water containing loads of chalk, and no doubt other odds and ends too!