What supply?
What step down regulator?
How are they controlled? (80mA can't be done directly from an Arduino).
Danois90:
Can the voltage drop be caused by overheating in the regulator
Most likely
Danois90:
or is the power supply being overloaded?
Without mentioning the type or at lesat a photo, no idea..
Danois90:
Or may it be caused by a third factor I have not thought about?
Same, without circuit it's impossible to tell.