A2-year-old toddler goes on periodic food jags in which she will eat only one or two favorite foods. should her parents be concerned about her nutritional status?

No because this is a short term behavior

Explanation:

If a toddler goes on a periodic food jags then her parents should not be concerned about the behavior because toddlers have this habit of liking and disliking food of different types.

Their taste buds start developing and they urge to taste different kinds of food but like on few of them for sometime and then shift on another food for the next time.