My toddler was also quite a picky eater, and we managed to transition from formula to full cream milk around that age. We started slowly by mixing the milk with formula and gradually increasing the ratio over a few weeks. As for nutrients, I focused more on offering a variety of foods rather than replacing formula with supplements immediately. My PD mentioned that if growth is on track and they are eating reasonably well, extra vitamins may not always be necessary. Every child is different though, so if you're worried about nutrient intake, it might be worth checking with your PD. The transition can take time, especially with picky eaters, so don't stress too much 😊
We switched to full cream milk around that age and it went fine, even though my son was quite a picky eater. I had to literally hold the box of UHT milk in front of his face while he drank it though 😂 Unless he was super hungry, he wasn't having it. It definitely took some getting used to!