You could, but there is a high chance that they might not reply back.
You are one among thousands and thousands who have been rejected and it does seem kind of pointless because asking for a reason won't get you an offer.
One of the main things to take into consideration is to say why you want to study the course? What skills do you have? Why is this your passion? Include extra curricular activities and roles. Always do other things related to your course outside of school hours, such as extra reading, attending lectures, doing online courses.