Maybe I missed it in the post(s). Whats common to the 2 tanks other than the electrical panel? Are they plumbed completely separate or together? Most of us at some point has probably gotten bit by stay tank voltage. Mine was isolated to a faulty heater. The grounding probes will help protect you but wont help you find the problem. But being protected is kinda crucial...lol. Its odd that 2 separate tanks would be experiencing this at the same time.