I would be most concerned with the watery droppings especially that you mentioned no odor. I remember having litter of infant puppies and their poo was so watery, their hindlegs were soaking wet. I lost them fast. Don't remember what it turned out to be. But anybird/animal can dehydrate rapidly from all the fluid lost. I wouldn't use human products, Pepto Bismul has salicylic acid (sp?? )which is aspirin. they may be overdosed on this, especially a tiny serama.
I could at least call a vet and asked what you could do for them