Grey & Black Tank Condensation

On my Travel Supreme 5'ver the tanks have overflows. First time I've ever seen that. Also the washer/dryer does not go into either tank, but straight into the sewer line. One more thing that surprised me.

Condensation is caused by a difference in temperature with water vapor that has sufficient humidity to allow condensation.

Two things seem not to support condensation as the main problem: 1) The water in the tank was allowed to sit for enough time to reach ambient, hence, little temp difference 2)The under belly material and surrounding insulation would deter high humidity water vapor from reaching the tank.
The above is not to say condensation is not an issue. You may have the rig parked in a high humidity environment, I have no way of knowing. I would be checking for another source for the beads of water.

raygreg: I did check the black water flush & it was not leaking.
I had no idea it was wet under the plastic/cardboard type of material. I opened it up to replace the 3" cable operated waste valve. The valve was not leaking, just getting hard to open & close & I was afraid the cable would break.
When I found the water, I opened up, dropped the plastic enclosure back 7/8 feet on both sides. The insulation was soaked & I guess there was maybe a total of 2 or 3 gallons of water trapped on top of the plastic enclosure material. The plastic was bowed down maybe a little but not like it was close to dragging on the ground. I dried it as best as I could and used wood blocking etc. to let air between the plastic enclosure material & insulation for a week, so everything was dry. After finding no leaks, I replaced the insulation & put the enclosure back on the sides, & left open the area across the bottom side to side, so I could see into the tanks. Checked a week later and found the beads of sweat on the tanks. I was parked on a concrete slab & never noticed any water or drips on the concrete.
I do what most do, keep the black tank closed & the grey open until a day or 2 before dumping the black tank. This didn't just happen over night, as we were in Florida for 3 months this past winter.
I just wanted to know if anyone else has noticed this. I had no clue and would not have known if not for opening it up to work on the valve.

No answer yet? Did you check your black water flush (If you have one).? That may be leaking. Are you sure the insulation was all dry after you dropped it? Are these beads of "sweat" with the bottom sealed up or left open?
Maybe a fan to circulate some air if with the bottom sealed?
I give up, I've never seen this before, or looked for this type of problem.
Good luck fixing this. Let us know if you find a solutioin.