Ringnecks and too much sunflower seed

[ringnacks]

Hi today I went to my local pet shop to ask about why my ringneck could be pulling her feathers she asked me a hole lot of questions and one of them was is it with another bird and I replied yes I was coming in to by another cage to separate them. As we went back to the counter so she could see me a book full of cages that they get in, one of the others ladies out the back asked what was wrong as I told her my ringnack is pulling out her feathers and the feathers are looking really bad, (like they are fraying out at the ends) she said I would think about putting them in different cages and when on to ask about the cage they are in now so I told her it was a big 6ft high cage and was in the shape of a hexagon and from side to side is about 198cm apart, she went on to ask about the food I was giving them and where I got it from I told her normal bird seed and some fruit and nut she then took me over to their food and asked if it look like theirs and I said the normal seed yes but our fruit and nut is like 78% sunflower seeds. She then went on to tell me that having to much sunflower seeds are bad and it can cause the pulling because of to much oil. she then showed me some Vetafarm products and told me to look it up and come back when I found out more about it as she didn't what me to think she was trying to make a sale, she also showed me a spray that stops them from pulling and said she wasn't going to let me leave without it (which was ok with me.)
Anyways my question is: Is it true that too much sunflower seeds can cause the pulling of feathers?