I have seen this from time to time as well - with one device, always the same one. I believe in my case this device is having a hardware issue and a device is starting to fail. That makes sense as the activity is all internal to that specific device, so HA would know nothing about it other than being able to report that it’s state had changed.
In your case however it seems to be multiple devices at the same time (which would make a hardware failure very unikely unles they are all controlled by the same piece of hardware)?
Also: what in HA doe all those lights have in common? Are those lights members of a group or a scene that is somehow acted upon that is not for some reason reported?
The first question I always see when someone reports similar is “do you have any Amazon Echo Devices?” If so, do you have “Hunches” enabled? For some reason, someone at Amazon thought that feature should be enabled by default.
Start by checking what those 3 lights have in common which the other lights don’t have.
Controlled by the same (smart) switch? Same model? In a group on a third party app (like Alexa)? Lower wattage?
Narrowing down the commonalities will help you isolate what is causing them to turn off