What are the chances of a hole being in a 4 month old tank?

I've been trying to find this leak that I have in my tanks and can't find it for shit. I can't hear anything or see any bubbles when I spray everything. Could it be that one of the tanks has a hole in it? it leaks about 1 lb every 5 min which isn't much but is a pain if it sits around overnight (0 PSI) or for a few hours. The tanks are 5 ga. Hoosiers.