There are a few nudibranchs I've encountered but haven't been able to identify.
Unknown #6
Maybe chromodoris?
Unknown #5
Maybe glossodoris?
Unknown #4
Likely a chromodoris or maybe nembrotha
Unknown #3
Maybe really a flatworm?
Unknown #2
This looks like a glossodoris or maybe chromodoris but I can't find a good match.
Unknown #1
This might be a Pteraeolidia ianthina, but it's enough unlike the other photos of that critter that I'm not sure.