Poop and being in poop is normal for ducks. They are not like puppies or kittens where you need to clean up after them constantly. I am encouraging you to relax your cleanliness standards because the frequent cleaning and bathing may be making things worse. Ducklings are routinely reared outside by mother ducks who don’t wash them every time they poop. The oils in their skin and feathers are an important part of their natural protections and washing them off too frequently can strip them of those protections, while also lowering their body temperatures at a time when they are developmentally unable to maintain an adequate body temperature on their own.
This was counterintuitive for me, too, because as a mom, I show my love and care by keeping my kids clean and our home clean. But ducklings’ needs are different. They need warmth and the ability to move themselves closer and farther away from the heat source, since they can’t regulate that internally until they are fully feathered. That’s why it is common practice to move the heat source a little farther away each week as the ducklings grow feathers over their down, lowering the temperature by about five degrees each week until you reach the ambient temperature and the duckling have the full insulation of feathers.
Just as we feel cold after exiting the shower or if we end up in wet clothes because we are losing the heat necessary to evaporate water from our skin, ducklings have to use body heat to dry their wet down. Doing this over and over makes it extra hard for them to regulate their body temperature.
When I understood their particular needs better, I got more comfortable with cleaning the brooder daily instead of constantly, giving just one bathing opportunity per day, and focusing on having a heat source that allowed my ducklings to choose how warm they needed to be.
I hope this helps.