Help with current

I'm making a clock that uses stepper motors and timing belts instead of your typical clock assembly. The housing will have 5 or 6 leds. I've been focusing mostly on code, but ran into an issue I haven't seen before. My setup as of now is an Arduino nano, 1 (for testing) ws2811 led, and 3 28BYJ-48 Steppers driven by ULN2003 boards. Everything except for the led is hooked into a spliced usb cable in a adapter that puts out around 3 amps at 5v. The max draw of all 3 steppers should be around 400ma. I ran a test that moves the motor and changes the led color and when the stepper rotates the led actually gets brighter. My first thought was current drop, but why would it get brighter? I have to get a new fuse for my multimeter, but was able to test voltage and it is dead consistent. I know capacitors are used to smooth voltage is this true for current as well? Any other suggestions?

. My first thought was current drop, but why would it get brighter?

Well not current but voltage drop.

It gets brighter because a stepping motor draws the maximum current when it is stopped. When it moves it draws less current.

So it looks like your power supply or the way you have wired it is not up to the job.

Without a circuit diagram it's hard to be helpful. Please read 'how to use this forum - please read' and follow the instructions for posting circuit diagrams.

Was able to test voltage and it is dead consistent.

Please remember that a multimeter averages the voltage so quick changes will not show up.

High current low voltage circuits need thick wiring and decent connections as a small fraction of an ohm will be very noticable like this.