Overshot OG . . . Again

I just put schwartzbier in the cooler today. Jamil's recipe. I did Noonan's decoction schedule using Beersmith. To get to 1.051, I had to top off to about 6 gallons. I have blow off tube because of lack of headspace. Did my see it coming. (I know, the definition of insanity is to keep doing the same thing and expecting different results). I have been afraid to use a 78% efficiency rating in Beersmith in case my run of luck craps out. Topped off with about a gallon and a half of bottled water that I did not sterilize first. I have been overshooting since I started milling my own. I'm hoping no nasties living in the bottled water.

You should be fine. Yeast protect their turf.

Consider cutting your batch back to a 5 gallon?

or adjusting to 75%