Gothic Arch Bow Shed Floor Frame Joists

Floor Frame: Twelve 4' x 4' boxes made with 2inx8in x 12ft joists. Filler joists in the center of all 4x4 boxes are made with scrap untreated 2x4s - stacked 2x2 pickets. The pickets are treated lumber. A couple of the 2x4s are untreated. I made a DIY wood treatment out of water and borax sprayed it on any untreated joists then added a quick coat of old polyurethane that I had.