I assume that this is a Hub 3, no? There seems to have been a big uptick in reports of this issue recently, and that's not surprising as these hubs weren't exactly built with top notch components and LEDs only have a finite lifetime, so it's not too unusual for lots of them to start failing at about the same time.
The red light is supposed to be a sign of overheating, BUT it is also likely just to be a case of the LED itself or the sensor failing, especially if the hub doesn't seem unusually hot - but it does need replacing, because if it WERE to overheat in the future, how would you know?
Many people also report that their connection seems to have gotten worse, this is almost certainly coincidental, your connection was probably bad for some time, you just didn't notice it, but the red light makes you more conscious of the connection. It's human nature to try to connect things which really are just coincidental.
In a day or so, a member of the forum team will get to this thread, ask you to do the full factory reset, turn it off and on again dance - which it seems like you have, and then message you directly to get some details and arrange a swop out. Now there is a good chance that what it is swopped with is might also be of similar age, so you might be in the same situation again in a couple of months!
