Freeze plug problems

[X66 714]

I noticed I had a coolant leak under my ss396 Camaro that I just had at MCACN in November. I didn't rebuild the engine because it only had 41k on the rebuild. I did change all the freeze plugs because I had one leaking. I used the green coolant 50/50 mix with tap water. I've probably only driven the car 3-400 miles since the restoration. I now have three freeze plugs leaking. The one pictured is one I just removed. These were brand new less than a year ago. The battery is never left connected when in the garage.

I sent this picture to my friend Larry (lbnaz) & he indicates that it's most likely a ground problem causing electrolysis. I guess I need to check my grounds but I wanted to ask if anybody has seen this & maybe, where was the problem found?
Thank you, Joe