what would eat a GBTA, 6line wrasee, yellow clown goby?

[kien]

Powerheads eat GBTA. They seem to love the.. nom nom nom nom..

Not sure about the rest. Your tank is pretty new so I'm not sure anything ate them. They likely died and got "cleaned up" by the clean up crew. Happens all the time. Some people have had 5 inch tangs go missing over night

The other possibility is a bad hitchhiker like a mantis shrimp. Try to set a trap with bait out to see if you can catch some.