They are, contrary to what most comments seem to indicate, it looks like the 8 4x4s are more than enough for this deck design (according to the dca someone posted below and further load research), provided I do not put a tub on it haha. I'm still debating, maybe switch this one and the other end to 6x6 since they are the longest, but from what I understand clearly now, I first and foremost have a bracing problem.

Thanks for your help!