My ST-S had a leak from one of the lower hose clamps early on, and the dealer replaced it.
Your pic looks more like the reservoir tank itself may be leaking, possibly due to a small hairline crack.
Alternatively, it may be that the cap on the tank is not completely closed or is the source of the leak.
Check yourself or bring it back to the dealership!
Are you sure it's leaking ….. that is the seam where the parts are glued together … if that seam isn't wet, I think it's dried glue / sealant ………….. I have seen some tanks ( before the Ryker ) that actually split vertically, but most leaks are at the connections …… good luck … Mike
Definitely a leak there somewhere, that's dry coolant splashed on the doodads (technical term) underneath the tank. That's gotta be a warranty job considering its age.