shubunkins chasing each other

we have had my daughters shubunkin for around 8 months… we finally upgraded to a bigger tank and decided to get another one to keep it company - however we’ve had for around 1 month now and our old one chases the new one, literally darting around the tank after it… and then sometimes they are happy to just swim next to each other and follow each other everywhere ?

our older fish, seems a bit more on edge - in its old tank it was very docile and swam around quietly but now seems to swim erratically on occasions.. i don’t want it to feel stressed as i’ve done everything i can to keep it going (had fin rot when we got it , bloat and icy after buying new plants for its tank 🙄 etc )

been keeping an eye on the new fish and there is no damage done to it so i have no idea if this normal?