ADHD diagnosis

Hi all!
bit of an odd one but I was diagnosed with ADHD about halfway through my exams this year after it has been affecting me quite badly but I haven’t stated this on my UCAS application as it was sent off before the diagnosis.
Is there any point emailing my firm and insurance to let them know now and to see how this affects my offer? I haven’t had any access arrangements through exams as the school had no idea so i’m worried it has affected my grades but I didn’t want to piss off the admissions by emailing them if it wasn’t worth it so I was wondering what people’s opinions on this were?
Thank you!