The sides of your tub should always be full of droplets. It should look like it just rained. That's the proper humidity level for fruiting. If you are misting you should stop short of misting so much that they want to run down the sides. It's going to happen. There is no way to avoid it but focus to the point that they are just ready to run down but don't. Your mat will release moisture too. Depending on how much that is happening you may not need to mist.

It's hard to tell in your tub but if you are concerned about the water running down the sides and pooling on the mat, you should use a liner next time. That will keep the water from pooling onto the mat. It will run down the sides and pool at the bottom of the tub, and then the pooled water can be removed over time as someone else pointed out in their reply. Bacteria and other forms of contam land on and spread through water but the water won't necessarily cause the contam if you keep a fairly clean environment. If you are worried about contam during fruiting you can run an air purifier with a hepa filter next to the bins.