If the veins aren't too big I do assist them carefully out at this point. I have 2 that started panting that I didn't help and they died. I swore I would only help if they did this, I have helped 3 since and they all lived. I have been hasty and lost chicks "helping" , but would help if I were you
check this out https://www.backyardchickens.com/forum/viewtopic.php?id=9316
check this out https://www.backyardchickens.com/forum/viewtopic.php?id=9316