@tanguatlay,
Obviously, CI is terribly confused, Ms Tan, as is Lustig Andrei. They throw around these terms like 'colloquial' without ever really knowing what they mean.
At one time they'll disparage language as colloquial, now they are saying 'fine' is not colloquial.
Have they offered you anything besides their opinions? All McTag has offered is him obfuscating.
When something doesn't sound natural to native speakers, it leaps out at them. As you've used this numerous times without much ado, it seems that these "native speakers" just want to jump on the McTag bandwagon.
Except for CI. He wants to jump on then jump off then jump back on, then off, then ... .
Here's a Google exact phrase search for
"Are all of them fine?"
About 1,630,000 results
Again, I'll say that it isn't the most common collocation, but that doesn't mean that it isn't used.