Mildew

Thanks. We don't have any wet spots or leaks. What could be the cause and remediation thoughts would be welcomed!!
Thank you so much

Esp on baby items, you'll see this in garage-stored items too. The mildew "feeds" on the baby sit up--I've noticed it mainly on items like carseat straps where a baby spat up on it, but was difficult to wash out (you are never supposed to "wash" straps). Wipe it down with a detergent solution and put it in a conditioned space, and it should be fine again.

Mildew is generally defined as mold/fungus feeding on fabrics and leather. It thrives in homes in the presence of moderate to high humidity and the absence of light and air circulation. The moisture may be coming from condensation on the concrete floor slab and foundation walls if they were not insulated and/or sealed from the outside. It is often necessary to run a dehumidifier that drains into a house drain. Get a big one so it doesn't have to run all the time.