Can swell at edges and lose strength when water penetrates bonded layers.
What changes first
Look for edge swelling, delamination and localized sagging. The pattern and location usually matter more than color alone.
Moisture and movement behavior
Record whether the material changes after rain, water use, heating cycles or seasonal humidity. A material can display the damage while the source is somewhere else.
Before repair
Determine whether the material is the source, a pathway or only the final surface. Correct the controlling condition before replacing finishes.