19% is far, far too low. The air in most people's houses or outbuildings usually has a lot more humidity and that's why for some incubating dry for the first two and a half weeks is viable, but if the air in the room your incubator in is so dry then you need to add water as in the incubator it only gets drier, the incubator is not the same as a live animal sitting on slightly damp ground.
At 19% the egg will loose too much moisture (osmosis), the air cell will consequently be too large which leaves the embryo with not enough space to grow, so come hatching time it will be small and weak.
The incubators Shaum Hammon referred to must have been in a room with ample moisture in the air to get away with not adding any water at all. Unfortunately those advocating incubating dry hardly ever mention that their incubator's environment is one with sufficient humidity (they often don't even realise it), which puts novices on the wrong path. Luckily many people incubate in warmer months when humidity is higher anyway.
Waddy is right with how opening the incubator affects hatching, even a very short draft of dry air dries out that thin membrane and extra moist air doesn't compensate to re-soften the membrane again.
JayR, as it's only day 1 don't panic, though, just top it up today
You'll find that with better weather (promised for the weekend?) humidity in the room will go up automatically, which helps. I've just hatched 19 out of 20 eggs last week and have the Mini and the Octagon full again now. Busy days