I've never heard of Solar servos before, but find the spec info rather bizarre.
Usually servos are listed with 4.8-6V power range.
Also, speed = email@example.com
doesn't make any sense to me. What's the units of 0.1?
Miles per year????
Also, you should NEVER EVER EVER power your servos from the Arduino 5V pin.
Use a separate battery.
Also, "straight from the arduino board - which I believe is 5v" --> umm, so you
don't even know what voltage is being applied. Bad dog! Get a DMM.
Also, as they are digital servos, they may just require a different pulse protocol
than the Arduino puts out. Who knows?
So, take your pick as to the problem here. I would first try to track down better
spec info, as they are some off-brand thingamabobs to start with [at least in my
hemisphere of the world].