I experienced something weird as well on iris that's why I have to abandon the platform and move to amethyst, plebstr and primal.

Iris.to and nostros have been reported to wipeout your following list.

https://github.com/KoalaSat/nostros/issues/518

Thankfully the people I was following were cached by amethyst, which restored them.

https://metadata.nostr.com seems to fix this, however I don't see a way to upload it's backup Json file.

There are other tools which will back up your nostr, I will post them in the replies.

Nostr backup tools.

https://metadata.plebnet.dev/
https://nostryfied.online/
https://metadata.nostr.com/
https://kind3.xyz/
https://nostrsync.live/

I experienced this twice with iris. Restoring through Json didn't work. I have had no issues with primal.