What is your soil, jojoe? These are epiphytes, which originate high in tree tops, so if your potting soil has manure in it, that is something they haven't adapted to. They like really aged compost, made with leaves or other organic matter, and prefer something really fast draining. Other people have suggested fertilizer, but there is nothing wrong with the color of your cuttings, they are nice and dark, so I'm not convinced that giving them more fertilizer will help at this stage. They also dislike any kind of minerals in the water (high in the trees, they would only get rainwater), so if you have the chance, capture some rain water, or even buy a bottle of distilled water from the drug store.
