High fibre diet for dwarf hamster?

[PurpleKat]

My little dwarf is getting close to 2 years old and is getting a bit more elderly visibly.
She currently has Harry hamster mix, with added small seeds mix, and mealworms. Also, fresh veggies, while I'm doing dinner she has bits in the evening. Also once a week or so, dried forage, with flowers and leaves, cooked fish, chicken and egg.

https://www.hollandandbarrett.com/sh...9?skuid=083438
Similar to this but more variety of seed (I checked and all of them were safe)

For treats, once a month or so, the whimsy chew with yeast for B12, dried fruit, a couple of whole walnuts.

For older hamsters I read they need more fibre, what could I add to her diet.