Why is my iPad not charging?

recently my 2 iPads have stopped charging using the factory charger plugged into an outlet. But when I use my wife's apple charger it works. I've tried new official Apple cables and transformer to no avail. Sometimes when I try with my chargers it flashes back and forth rapidly from "charging" to " not charging". In some cases I have left it plugged in overnight when it said "not charging" and yet it did charge to 100% But then last night it didn't. Thus is happening on BOTH of my iPads.

I have cleaned the plug and socket. I also have restarted using both buttons. This is weird.