Woah. Was in the process of transferring domains, hosting and DNS for a small local org to another agency taking on those responsibilities.
Apparently the transfer to them has been "reverted".
Nameservers are back with me and only working by chance.
I'm the only contact on the hosting account now.
I was NOT consulted about this.
Just as well I'm a good egg, eh? But even so, this is super bad.