Found answer to my previous post:
Hi Irina,
we have this document which will guide you through the process of using our Custom Fields Addon:

https://www.jevents.net/docs/club-addons/item/adding-custom-fields-to-jevents-and-club-addons

Once you create a new field, you will notice an option called " Allow override of value when editing specific repeats" Set it to "Yes" and your event editors will be able to set different options per repeat