Steve, you have pics? Regardless, if more than one tank has leaks then:
1. Are the leaky tanks of the same OEM?
2. Did you get the leaky tanks from same source (whether new or used, just need to know if from same source)?
3. How much flex and why using shelves that flex? (Note: I'm not familiar with flex racks)
IMO, scrubbing would not be cause.