crushton - There is a grey and black tank side by side under the pass thru compartment & convenience center. They run longitudinally to the RV. Usually the black is on the drivers side and the grey on the passenger side. But to be sure, look in the pass thru and see where the toilet line comes down.
You are going to have to drop the coroplast to see where the actual leak is located. Most likely a cracked tank or a poped lid (I think the 2017 still hd the 2 piece tanks).