I thought the Day's goby and Tropical sand goby also looked quite similar. The Chinstripe goby seems to have more protruding eyes than the ones you have. I'm sure someone will have the answer but I'm stumped
I don't think baby Knights. Baby knights have the same patterning as the adults. I would guess somewhere in the Mogurnda family, not sure which but they resemble them. Anyway, hope this helps and good luck!
The purple spotted goby is generally (this is why I hate common names ) the same thing as Mogurnda mogurnda. Look that up and you will see the common name as Purple Spot Goby/Gudgeon! Hope this helps and good luck.