I only completed one semester of Art 3 and I decided to transfer out of the class at the start of the second semester. (too difficult and not a graduation requirement)
Am I supposed to inform the colleges I applied to and got accepted to about my schedule change?
Yup. For most colleges, it probably will make no difference, but they will still want to know.
Agree, it is best if the college you decide to attend is not surprised when they see your final transcript. I’d inform them now in writing and ask the college to confirm that it will not impact your acceptance (which i highly doubt it will).