Not fighting.
These birds are begging because they are hungry and will go to any beak they see for food, including their brothers who are doing the same thing.
Confirmed by empy crop in the second video, and smaller crops in the last two videos.
This is problematic because at this age their beaks are fragile and can be bent, broken or damaged by each other doing these motions.
Be sure you are feeding these birds correctly. MINIMUM 10% of their body weight per feed, or more until the crop is full.
Very important that the consistency is right. A formula that is too watery will result in hungry birds even when there's still something in their crops, they will beg more, won't sleep more and can suffer badly from malnutrition.
Double check everything - birds weights every morning on an empty crop before feeding, as well as the formula consistency and temperature.
At this age, these bird will eat and then make cheep away while they fall asleep within like ten minute of being fed.