Should I give reasons for my amendments in UCAS application in email to Universities?

Hi, I have made amendments to my UCAS application. The amendments are relating to retake of subjects. Right now I am emailing my Unis to let them know of the amendments. Should I also provide them with reasons for the amendments, or should I just let them know of the amendments?

That depends on the reason

My reason is that I wasn't feeling well mentally due to the ongoing pandemic situation. Is that an acceptable reason?

If it was just an error then there's no need to go into the reason.

Have you had confirmation back from UCAS that they've updated your application? Do NOT email your universities to notify them of a change until that change has been confirmed by UCAS (otherwise you'll need to email them twice)