Diagnosis was that my well was losing pressure because it had a problem - I opened may faucets in my house at the same time to try to mimic the pressure loss i encountered during my sprinkler cycle - I did not experience it - and my well is performing as it always has with my household fixtures - so I spent $70 on a brief service call and am back where I started. They guys that came out were nice and professional- but I'm not convinced its a well issue based on my tests in the house