P0304 and P1121 Related?

Only relation is they're in the same vehicle.

Try swapping, and check for oil on the plugs and cops.

Has it been raining lately?

Here is the work up for DTC P0304 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/2054m/cip0300.pdf

Here is the work up for DTC P1121 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/2054m/cip1121a.pdf

 

The tip of the plug looks dry, but the picture makes it hard to tell. If those happen to be the original plugs w/355k, replace them all.

You may have a water leak in the spark plug wells, and or a valve cover leak, is the liquid on the socket greasy to the touch?

Check the windshield cowling drainage holes, as that can be the cause for water intrusion.

Clean the plug, clean the COP (coil over plug), and clean up the spark plug well before reinstalling the new/used plug.

Does the engine oil on the dipstick have the same visual appearance as the liquid on the socket?

 

Is that miles and not kilometers (no location in your profile), either way they should still have some life left.

Not always, sometimes it can be a localized leak. You might try retorquing the existing gasket before replacing.

Clean up the spark plug well and coil before installing the existing plug, then try to locate the potential water ingress point.