My 3yo is picky in the sense that he won't eat anything with sauce.
Or cheese. He is so picky about what he eats, sometimes I worry but other times I just stick with it.
The 20mo is better but still picky.
I find dinner the most frustrating. But I know sometimes they will touch nothing, and other times they'll eat a lot so it balances out.
We give a vegan multivitamin, can't remember the brand. It's just kind of my backup and reassurance that at least they're getting something. I also make them smoothies with lots of supplements in them, however atm they are hardly touching those.
My big thing is I will not cater to them or make specific things. So I carry on planning our meals for the family, and if they eat it they eat it. Generally they do much better at breakfast and lunch so I try to focus on those a little more, which is tough because those are the two meals that I have the least amount of time to prepare!