I would say not yet. Actually, it's day 19 for you. Day 1 is not until the first day after you put them in the incubator. (If you put them in on a Monday, theoretically they should hatch on a Monday - 21 days later) The 21 days is a guideline - not a definite rule. I've had chicks hatch anywhere from day 18 to day 23. If your incubator thermometer is even a little bit off and it was running cooler than you thought, that could set them back a day or so. I wouldn't worry until you've gone a few days past when they "should" be hatching. I also would not be taking them out to candle them, water candle them or any other such thing until that time. The more you mess with them, the more chances of them not hatching, in my opinion.