Give the chicks a chance. Sometimes after they pip, they may not zip for awhile while they are absorbing the yolk. After the chick has been pipped for around 24 hours then you can check and see if it needs assistance. If you do assist and see any blood, stop and wait awhile. Usually if you try to assist too soon after a pip the chick may not be quite ready to hatch. The chicks can hatch a day or two early or a day or two late depending on how steady the temperature has been. Humidity is another issue. If you need to go into the incubator, you can always mist the eggs a little with warm water and that will bring the humidity up quickly but then sit on your hands again and let it stabilize. I usually incubate under or around 40% and bring the humidity up to around 75% during lock-down. I just had a hatch on Tuesday. My next hatch is in a couple of weeks. Good luck and have fun...
Seems so far like just a late hatch. Waiting to see if the other two eggs will pip as well.