I had a weird event happen to 2 liquid fertilizer tanks on my Kinze 3600 planter. The tanks are 3 years old, vented, and new saddles for them at the same time. They hold 150 gallons. I was filling the tanks with 28% nitrogen and zinc for starter. The tanks had about 120 gallons in each tank. One tank collapsed about 1/3 of the way while I was checking the planter. A few fillups later the same thing happened to a second tank. I have no idea what caused this. The planter is always stored inside. Left the planter set out in the sun for 2 days and one tank returned to the original shape. Left the planter set out a couple more days in the sun and the other tank returned to the original shape.

I am puzzled to what caused this to happen and what caused the tanks to return to the original shape. Any ideas? Any thoughts on how to prevent this from happening again?  Thanks, Jim