Decks, Patios, Porches and Docks - Improper deck board spacing

I have a rooftop deck above my condo which was built out in stages. The initial contractors placed the boards tightly with little space. It is pressure treated lumber. I then built out planters, built-in seating, a raised deck area, and a pergola in the second stage with a different contractor who spaced the boards appropriately. When it rains, the water does not drain through some of the initial boards due to the tight spacing. I prefer not to pull up all these boards and lay them back down (cost, poor cosmetic result, etc.). Is there any other way to fix the tightly-spaced deck boards to improve the drainage issue and reduce the risk of warping and rot?

Do you want to put astroturf or similar on the non draining section and hope it drains to the better spaced boards?

Can you get a Skilsaw and make an opening between the non draining boards?

Welcome to the forums! How long ago was the initial work done? Fill out your profile so we know where you live. It makes a difference in our advice to you. For instance, here in the South, we jamb our pressure treated 5/4 boards to each other. Our climate will cause them to shrink to a nominal gap in a few months. Initially spacing them, here, will leave too large a gap later down the road.

You could use a plunge router with a straight edge to make a new groove between the tight boards and then go back with a small radius bit to give them a finished edge.