Looks like the just the paint cracking, had this happen on my first mossie after re painting it in 2 pack automotive paint. the decks flex the paint doesn't, causing the cracks in the paint.

you will need to rub back the paint to bare timber and re paint, you might have a stain in the timber now from the cracks, but that is not a problem.

Re coat with decks with a thinned down epoxy, give two coats sand back lightly and re paint with either marine paint or use automotive paint with a bumper bar additive don't know what it is called but it allows the paint to flex.