I am only concerned about the beam spacing below the spa. Again, 8 foot is stretching it for regular traffic, but then your joists are 2x8's, so being that size and then on 14 OC you might just be fine.
But, if you could pull up a few deck boards in order to place some concrete bags under the beam attachment to the posts that might be a good idea. This would give some additional support to that intersection where the beams are attached to the posts.
More and more deck builders are getting away from side mounting beams to posts because all that weight is now resting and based on those carriage bolts alone. If the beams were mounted on top of the posts, the weight of the beams is directly upon the top of the posts and so much more downward force on more space, rather than on two 1/2 inch bolts.
You did a good job in planning your deck but with your skills and planning, you would have done some beefing up if you knew then you would have a spa on the deck.