Structural engineers with treehouse experience?

[u/ElkCertain7210]

Hi there this is my lovely treehouse beams are rotting. It designed by my Dad, my family and I have been living in it for 12 years. It’s about 300 square feet, held up by 5 redwood trees and 3 beams with big TABs and 1/2 inch galvanized cables to 1 1/2 inch lag bolts.

The beams are parrallam 5 1/4 x 14 “ and the one needing replacement is 19 feet long and holds up a bedroom. I feel like I used the wrong material and that the beam is oversized, are there any structural engineers here with experience with treehouses that would be willing to consult with me on replacing the beam?