Maintenance of granite outdoor stairs, damp spots?

Hello everyone,

about 2 1/2 years ago we got a new outdoor staircase. In the lower area, the granite slabs were laid on the existing precast concrete slabs. Now, moisture is showing in some places, which barely goes away (except now in summer when it is warm). Currently, the staircase always looks as if moisture is coming up from below. Is there a product I can apply here so that the moisture does not come through as much? Or what can be done here?
Ps: I took the picture when it was generally rather damp. You can also see it in other places on the path etc. Nevertheless, these spots persist for a very long time, although large parts of the slabs have already dried out long ago.
Thank you.

That looks like moisture from above, which dries last in joints and small cracks. For roofing felt roofs, it would indicate leaking spots. The only thing to do is wait for it to dry, I wouldn't coat anything because of the risk of slipping. Our steps are 15 cm thick and each made from a single piece, they dry more evenly.

That looks like moisture from above, which dries last in joints and small cracks.
In the case of bitumen roofing felt roofs, it would be an indication of leaking spots.
The only solution is to wait for it to dry,
I wouldn't coat anything because of the risk of slipping.
Our steps are 15 cm thick and each made from a single piece, they dry more evenly.

Above these steps we also have solid block granite steps, which also dry evenly. But air can pass underneath them.
By coating I meant more something like impregnation, so that moisture cannot penetrate the stone.

The moisture is in the joints, you cannot coat there. And any coating on the surface will fall victim to the weather, but unevenly, i.e. new spots.