1 yr old leaking T/P valves

I have two water heaters that are about a year old now. I flushed the sediment out today and flipped the T/P valves to make sure they're not stuck and now they leak.... thee system is at 40-60 PSI (well system) and there is an expansion tank in the system. The first WH is set at about 90° ant the second is at 130°. There is a softener on the system too. The T/P's are rated to 210°. I've fiddled and tapped the handle but they won't shut all the way. I'm planning on replacing them, but any Ideas why they would leak at such a young age?

Replaced the T&P on one WH... there was a piece of plastic on the inside at the valve seat. Looks like a piece of visqueen from manufacturing to heep the foam out of the hole. The other T&P valve was closed when I went down to replace them tonight... Guess the rubber is stiff and just needed some time to form to the seat.

The good news is that I'm only out $12, have a spare T&P and no more leaking.