Are those two overlapping panels where you found the leak near the floor, or is it somewhere higher up?
If it's near the floor, it's probably the same source as your front leak, as it may be flowing to the rear by thrust force as you accelerate.
I once had water intrusion that wet the entire interior floor in this way. It was actually wetter in the rear, even though the source was in the front.
In my case, it was an issue at the cowl drain. It wasn't clogged or cracked either. The factory seal around the drain head, where the drain assembly meets the metal to seal it off, was compromised. I used Permatex Ultra Grey (the pressurized can version) to apply a thick bead of sealant all around. The finished product was much like the original factory seal in texture and appearance.