Will containers send requests to docker.io when they interact with each others

Really need help here.

Recently, I’ve been receiving emails from the company that is responsible for monitoring if any unusual requests sent from my server and the emails says I’ve been requesting to some IP a lot and it looks unusual, so I check on my server by entering command “netstat -s” and I found the sent requests has accumulated about 20000 ~ 40000 times per minute! I’m confused because I don’t think those tons of requests are needed for this server running ( the server is for IoT purpose and it receives data through mqtt servier, btw It has 27 containers running ) so I tried stopping all the containers and then the number of sent requests went down under 100 per minutes immediately ( i think the amount of requests is normal ? )
The company that monitoring this told me the requests are mostly sent to certain IPs and I went https://webiplookup.com/ to search these IP, it turns out they are mostly from “registry-1.docker.io” , is this normal ( tons of requests) or should I concern abt this ? and in what circumstance containers will send that many requests ?( I thought only using pull / push to docker hub will connect to registry.docker.io, no ? )

thank for helping me out.