There are good laboratories who do water testing, and also egg/ blood testing for poultry. our eggs went to the MSU Veterinary Path Lab in Lansing.
Some eggs from urban flocks won't test well, it's the old lead paint issue.
Mary
I too was concerned about your initial test with the rubber bowl, and I'm glad that more testing is clarifying the situation.
Recently I decided to send eggs from my birds to a testing lab to check for lead. Happily, the test came back 'less than 0.00025ppm'.
Terrific! And we do use rubber...