I won't put any oak, especially bark in any of my ponds. Indians used to strip it and toss it in ponds for fish kills. Might not be it, probably not but no oak here. Concrete rip rap can be good, but it can leach out some nasties also. With that small death rate I doubt you made toxic soup. Transport and plant usually has some deaths, just the way it works. I might have to reread this but I did not see if you mentioned equalization.
When fish arrive they are usually stressed. It is the most vulnerable time of all. Three things that get them is temperature differential, lactic acid overload and ionic shock. Plus poor or rough handling. Just a few floaters is normal. I think you will be ok. Give them some time to acclimate to thier new surroundings and they will probably start feeding well. Good Luck, sound like a nice pond.
