My guess is coolant from water pump or hoses running to WP. Given the car has the plastic underbody panels, fluids can end up on the ground in places not directly under an active leak.
Remove the firewall behind the seats and take a look around. You can also run the car like this (its loud and hot!) to see what you see.
Remember that even though your WP is relatively new, you may have a leak from one of the bolts not being torqued to spec. Torque is only 7 lb-ft so if its off a little, you can get a leak.
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