Spark plug condition - was it the right time to change?

Hello!

I had some spare time today so I decided to change the spark plugs for my 08 Prius with 99,000 miles, purchased 3 years ago at 65,000 miles and unclear as to whether the spark plugs were ever changed or not.

The car was running just fine prior to the change, consistently getting 45-55 mpg (albeit with an occasional P0420 code), so I wonder if the change was even necessary?

For your reference, below are the photos of the old plugs, Denso SK16R11 Iridium. I'm also curious to know if the crusty tip of the plug is a sign of a future engine problem that I might have to deal with.

The new spark plugs I got were E3 3.48 premium plugs, incidentally.

Thank you!