What Food Or Medication Can One Try When A Toddler Refuses To Eat After Starting On A To Z Syrup?

My son is 3 years old.he is born in premature birth.In last couple of months he is not eating food like dal,rice, veggie as usual which he ate earlier.so i give A to Z syrup to prevent deficiencies and proper growth.After taking A to Z syrup in last few weeks he is not willing to eat dal,rice veggie etc.what syrup or medication should i given please suggest