Hi, thanks for using healthcare magic
If he has been previously well up to becoming a toddler, with no issues related to his appetite, problems passing stool, vomiting
then it is less likely to be related to his history of gastroschisis
Toddlers can be inconsistent in meals meaning that their likes and dislikes can change quickly but he should still have an appetite to eat.
Loss of appetite can be due to an acute mild illness such as the common cold
If he has no symptoms suggestive of this or any other mild illness you may want to take him to his doctor for assessment.
His doctor would be able to determine the cause of his decreased appetite.
I hope this helps