DS1 and DS2 have been sick with cold, chest infections, different viruses for at least the last 2 months. Now DS2 has a throat infection and is running a temperature of 40 through the night . He is on his 3rd lot of antibiotics, poor thing, and I really need some advice to break this cycle. They seem to be passing bugs back and forth to each other. I'm now giving them echinacea drops and vitamin c but would welcome any suggestions of how to strengthen their immunity.