Hi, don't be worried. First of all stopping giving unnecessary medications. If your kids don't have any health issues previously thn nothing to worry. Just provide them a good, balanced diet and let them have a sound sleep like 8  to 10 hours a day. In pediatric age group infections are common and getting ill can be frequent. For minor illness they can be treated symptomatically.

I understand, nowadays situation is being tough for children. But all baby will have to learn to resist the situation. Don't give supplements like immunity booster too much, even avoid unnecessary medicine. Only give fresh and healthy, natural diet. Send them school, if affected give them rest, again send the school, it will lead to development of natural immunity.