Leak under kitchen sink

We're just back from our 4th outing in our new Trailmini. On the initial trip home, we found a leak around the drain in the sink. At home this was sealed and everything has been fine for 2 more trips out. This time, I'm getting water in the same area but can't find anything wet in the plumbing lines, around the drain or under the faucet fittings. Luckily, I have a large oval plastic tray under this area which has been catching the water! The refrigerator is to the left of the sink cabinet and we looked at that as a possibility. No moisture.

We had a very rainy Friday night and somewhat soggy Saturday; It was 39 degrees last night so we had alot of condensation inside with the heat running. Is it possible that is the cause? It was at least 1/4-1/2 cup of water in the tray. Where else do we look? It's extremely cramped getting under the sink so there is no visual of the faucet connections. Any suggestions would be greatly appreciated!

Judy
2010 Trailmini
2007 Buick Rendevous TV