According to Goedjn :

I'm fairly sure that GFCI breakers have a limit to how many downstream
outlets you're supposed to be able to feed with them. (four, maybe?)

I've not seen any that hint at such a thing in their instructions.
There's no reason I can think of where that would make any sort
of sense. They have to be rated for 20A passthru, otherwise,
you couldn't use them at all. The detection circuitry has no way
of knowing (or caring) about how many outlets are downstream of it.

If they somehow did have such a restriction, I suspect that
they'd fail UL/CSA approvals.

But who knows, perhaps some manufacturer does have that in their
instructions to try to trick you to buying more GFCIs than you need.

It _would_ make a certain amount of sense to limit the number of
outlets beyond each GFCI in order to minimize the number of outlets
going dead when one trips. That's a useability issue, not a safety
or operability one.

If I was going to live in the house, I'de replace all of them.

I'd test 'em, and if they tripped properly, leave 'em alone.

Another thing to check is whether you've got armored metal cable
that's grounded, in which case, pigtailing the receptical ground
to the box may be enough to satisfy the house "inspector"s little
LED tester. (Whether that's safe or code compliant in your area
is another question.) My second-floor circuts are like that.

While the NEC does permit cable sheath as a ground, the CEC
hasn't for a long time, and I wouldn't recommend relying on
it unless there was no other alternative. Old armor can
get remarkably high resistances...
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.