Supplements/diet improvements for 7 year old dog?

[Onatree]

Our 7 year old dog is a female cross between a Shih Tzu and a Bichon Frise. She’s never had any health issues (touch wood) but we are looking to see if at this age there are any dietary improvements/supplements we could add for her. She was spayed early on and has never been pregnant, she eats a grain free kibble (whatever is available out of Millie’s Wolfheart or Lily’s Kitchen etc - grain free). I won’t lie that we/kids sometimes feed her little bits of extras of meat fish or cheese. Her weight has consistently stayed at 7 kgs throughout.

The main issue we see with her is that her right leg has always been a bit crooked but it doesn’t impact anything. No vet has ever raised eyebrows.

What if at all could or should we add for her you think at this age? Would a couple tins of fish a week like sardines or salmons help with bones/Brain? Are there any specific supplements we should consider? Particularly thinking of bones and eyes of course but also general health/lifespan.

We can’t completely alter her diet to raw or anything by the way so looking for tweaks and additions rather than a total shift of food.

Mobility supplements such as Yumove or turmeric with ginger. ; Yumega / Salmon oil for skin / coat ; Plaque preventative ( seaweed based) if you don’t brush her teeth?
My labs have had plaque off and yumega oil for a while now, and started the older one on turmeric a few months ago.
They are both healthy with very shiny coats and good teeth.

There's a joint supplement the vets often recommend called synoquin, but I would check with them rather than buy something rubbish. I don't think lots of canned fish is ideal, we often give ours healthy sprays so some Salmon the kids don't finish, but age 7 is middle age for a dog.