I made a group and I am getting an error with certain members. 

One says "You may only add friends to this group. Please send a friend request to xxxxxxxxx first". But I'm already friends with them. It has happened for two different people.

Next is just "unable to add xxxxxxxxxxxx to group as their account has been deleted". This one seems self explainability and since I've only gotten this message for one person I'm not suspecting anything but that they deleted their account. 

I heard a rumour that groups doesn't work on iphones?