Power shouldn't be the issue.
I can drive the Strip at full brighness and with all three Color values at 255 without Problems.
I first tought it has something to do with the 3.3V logic Level my adafruit feather M0 Outputs, bit when I'm using the static 10 on the red value it works dimmed.
Also what I found out is that the red value has to be cranked up in order to make the Strip work, it won't help if i set green or blue to a static value