My 10-year Old Daughter Ames Gymnastics. She Has Gotten Sick

My 10-year old daughter Ames gymnastics. She has gotten sick 3 times of which the last time, she was severely sick - lost weight, felt really weak, congestion in her nose, when she laid down she complained of being dizzy and had a low grade fever. Where we live pollen is an issue but because of gymnastics we think there is a connection. How can we determine the cause of her being sick?