Help!

Hi ladies! I have two sons one is 3 and the other one is 2 , they've reached a point where they don't want to eat i tried everything but they just don't want too , what can i give them (besides food obbiously) just to make sure theyre getting the vitamins and nutrients they need... They used to eat everything idk whats wrong now that they just stopped they eat so little and im worried. Please help tia!!