Well, got confirmation the front driver side air strut has a leak. Shop said dealer friends mentioned that the front left has a history of going bad before the others. They didn't say why.

The clunking sound was from the strut being so low it had no more travel.

Having them replace both fronts with struts from Arnott Industries. Cost for the struts was $399 each plus $38 shipping. They supply you with a UPS return label to return the cores and you receive $100 credit for each core returned.

They mentioned that it would need a ride height adjustment afterwards but I said I'd take care of it myself, of course.

The rear left was low too but they said that it would probably go back to normal. They said the 3 others were tight and held pressure. I hope so.

I think I'll bring the ride height back to stock just in case that's what might have led to the premature failure.

I'll update once I get the X back from the shop.