My S had the diagnosis, and I would not recommend to write about that on an essay.
They are looking for unique personal interests, accomplishments, experiences, thoughts.
ADHD diagnosis is not as unique as it once was, and likely came off as being overly focused on grades.
Colleges do look for an upward trend in grades throughout HS, the reason you should leave them to assume
you became a better student, however you accomplished that.
Of course they should not discriminate, but a high ACT is no guarantee of admission.
What college is it that you think is so easy to gain admission. Many people with such high ACT
scores think anything other than Harvard/Yale/Princeton is “easy” to get in. Not true of many colleges.