From the photos, the chicks look fat and healthy, a testament to their parent's parenting skills. I suspect the four hours until their next meal was more stressful on the parents (they being so agitated) than on the chicks. At this age, they can wait this long and longer between meals without difficulty, particularly since there are only two at this site, their is more food for each at each meal anyway.
Just as a note, bander or predator, the parents' response would likely be the same, so if they were anonymously living on a cliffledge somewhere and had a close call with a predator, the chicks probably would have had to wait the same amount of time before their next "snack".
