Dear Leigh,
Interesting observation, thank you. Where do you live?
Where did you buy theese oranges/do you know the brand, or where they where 'prodused'?
I have since years warned people about chemical citrus;
I always said; Traw them away! Don`t use any chemical treated oranges, lemons or grapefruits. Don`t ever use the peel for cooking-preparations, it has to be organically grown.
Children are especially sensitive to chemically treated fruit; they often get allergic skin reactions while eating them, and maybe many years after. Bananas are also crap; don`t give your child green poisoned bananas; Organically grown bananas and citrus fruits is the only thing eatable!