I’ve had tires that just lose air. voth the Yokohamas and the Michelins on my vehicles now lost a lot of air when new, but it was consistent among all 4, unlike yours which is just one.
spit test on the valve (done), soap on the bead, and a deep cavity search through every inch of tread for a screw or nail (soap helpful there too). and if nothing shows, I’d probably air it up weekly until something changes. I’ve been surprised how sneaky some screw/nail punctures have hidden before I could find them.
the Michelins I have now were loosing 3 psi per week for a month when new.