Pellets v mixed

My vets say pellets are better than the mixed food so they gte a balanced diet, which is the best brand to feed neither of my two will eat any hay and one has teeth problems.

Pellets do avoid the problen of selective feeding but no pellet alone can provide enough of the right type fibre for healthy teeth or guts. The bun needs to be spending hours per day grazing on long fibres for correct dental wear.Crunching mix or pellets won't do it. They need hay or fibrous grass.
You may find the buns will start to eat hay if you gradually decrease the quantity of mix (don't do it suddenly because the bun needs time to adapt to the change). At the same time you can gradually start to mix in some pellets and reduce the percentage of mix -do it to suddenly and you risk upsetting the delicate gut balance of the rabbit.
If you haven't already, slowing introduce your rabbit to fresh grass, particularly long, course 'wild' grasses, gathered away from chemicals, dog poo/wee, or wild rabbits.
Some pellet brands worth trying re Science Selective, Allen and Page, Excel

Up until I found this wonderful forum my bun Peter was eating a mix food and hardly any hay although he did eat grass.

It took a month to change his diet. Now he has a small handful of SS pellets in the morning, constant access to fresh hay and fresh veggies in the evening.

He was a very fussy bun so it took a long time to change him over from the mix and I almost gave up but then one day he just decided to like it! Now if I top up his hay at the same time as giving veg or pellets he goes off to eat the hay! This would have been unheard of a few months ago.

I would say, do change your bun over but very slowly and with lots of patience. I never thought it would work for Peter but it did!