As Hello_Kitty_enjoyer mentioned, it's not abnormal for these canes to be smaller at this point. You don't mention where you are located but I am assuming you've got a long way to go in the growing season, at least 2-3 months.

I'm sharing some photos of my raspberry bushes at different times to demonstrate. The images are in reverse chronological order. Currently, I've got new shoots coming up everywhere. It's wild. It can take a few years for them to become established so don't worry too much the first year they are in the ground.

Photo dump

Some varieties fruit on the primocane too, but it sounds like you know that they don't. Do you happen to know the variety you have? This will help you better understand what to expect. New growth comes from different places on different varieties. I grow two varieties that behave very differently and it's a little confusing to see them side by side to be honest!

If they are in the ground they will need less feeding than in a pot. When in a pot they are in an artificial environment and can't source the nutrients they need. I don't really have to feed my raspberries at all, but I might throw some alfalfa meal (nitrogen, to support green growth) or compost (grab bag!) at the base in the spring.

You shouldn't fertilize too close to the end of the season because you will be encouraging growth that might not get time to get hearty to the cold and will be damaged.

Good luck and have fun!