In some cases, LED spotlights or LED lights continue to glow dimly after an upstream switch has been turned off.
One possible cause of this may be a live neutral wire. With portable wireless outlets, Wi-Fi outlets / Wi-Fi power strips, timers, and power strips with foot switches that have a single-pole relay installed, the LED lights or string lights plugged into them may continue to glow faintly.
What you can do:
In these cases, simply plug these products into the outlet the other way around; this should resolve the issue in most cases. If this isn’t possible—for example, because the flip cover is in the way at an outdoor outlet—a licensed electrician can swap the neutral and live wires in the outlet as an alternative.