Taylor Swift fans are apparently worried about her health because she happened to cough onstage -- which, while sweet, speaks to how hyper-focused these loyalists really are.

A video capturing one of Taylor's recent Singapore shows is making the rounds -- and at first glance, there's really nothing to fret about ... at least to the average person. Of course, though, Swifties were quick to notice that she briefly cleared her through while singing.

It literally happens in a second ... and she carried on afterward like nothing had happened.

And yet ... people online are pouring in with thoughts and prayers for Tay Tay, with many saying she's not well and that she might need rest. In other words, randoms playing doctor.

Like we said, she doesn't appear outwardly frail or sick here -- aside from the one cough -- but for some reason ... her fans seem to think they know all about her health, and it's weirdly leading to a lot of concern for the pop star. FWIW, Taylor's finished nearly all her shows.

It should also go without saying ... but she's a professional performer, and has been doing this for years now -- so if T-Swift was truly under the weather and unable to go on, she wouldn't. So, we're sure she might appreciate the sentiment here -- but it's unnecessary.

BTW ... this isn't the first time Taylor's fan base has openly worried about her. There've been other instances where she's caused angst among the Swifties -- whether it was over a missed mark onstage, almost tripping down some stairs or struggling to breathe due to the heat.

Luckily, nothing ever came from any of that ... but we suppose it's the thought that counts.