I am new but I use my Calendar & have MANY Recurring Events. If I understand you correctly, you are trying to edit info on one specific date of the event NOT change ALL the dates for the event.
Here is what I do:
1- Pull up Calendar view (Week/month..)
2- Click on the DATE of the event you want to edit.
3- Click "EDIT"
4- Make your changes
5- Click "Save"
6- When Pop-Up asks either *1time change or *change for all future dates of the event select 1 time change.
Sorry but just in case it helps here is what the screen looks like when I pull up my Calendar
And I click on the EVENT on the DATE I am wanting to change.