Hi, My Son Has 5 Enlarged Lymph Nodes In His

Hi, My son has 5 enlarged lymph nodes in his groin area, he has had 2 ultrasounds and 2 lots of blood tests which were clear. He got the first one after we had come back from Bali over 3 months ago and the others have just appeared recently. We are waiting for an appointment with a paedeatrician (?) but I was wondering do you think it could be related to coral or jellyfish? He is 13 and growing like a mushroom!
Thanks for your help,
Lisa Jones