Mama hens know. It could be that the other three are not viable. They could still be viable so what I would do would be to toss a towel on the mom so that you can get close and check things out without her freaking out.
Check the "crack" is it a crack or a pip ... Also that one of three eggs (lower left corner) looks like a pip crack (X) , check it. Careful when handling the eggs, keep it right side up the way you pick it up cause that's the air cell (fat side) side up...You could candle to check the 3 eggs.
How many eggs does she have under her? Ive had a hen kick out eggs before when she had too many so I try to keep it at 10 eggs under broodies. Ive also had them stop setting as soon as a few hatched, so now I remove chicks as I see them until all eggs hatch then either put them in a brooder or back under the hen