first Merry Christmas to you as well! second no question is stupid, not asking is. so you are off on the right foot!
twice i had that happen. what i did to resolve the unreachables was to begin with the app.
look on whatever device you have the alexa app installed on. open it and then upper left corner, tap on the three bars. then go down to settings. you'll see all your echo units listed in order at top left. look to see if under each it says they are online or offline. if offline try the old standard, power down your router. then unplug your 'offline' echo units. next power your router back up. once your pc, tablet or phone shows your wifi is back up plug those echos back in. after a few minutes go back into the alexa app(close and reopen the app to refresh data) see if the devices show as online now.
the only other two things that i can think might be related would be if someone had something running in the background preventing music from playing? even if you don't know what you could simply say to each unit, alexa stop. the other might be if in settings you have a 'do not disturb' time interfering with playback? i disabled our do not disturb function. so with any luck one of those will help out. better yet you've already fixed things and don't need any help