What should I feed my fifteen to eighteen month old baby?

Whatever YOU eat! Babies at this age eat like adults... They eat a lot and drink a little. Under one, they drink a lot and eat a little. Now, your baby should eat what you eat (peanuts are delayed until 2 yo, others if you have food allergies in family). Babies can eat any other foods, as long as they are mashable or cut smaller than the size of a pea.
Appetite varies. Your toddler will show an unpredictable interest in foods. Foods that you eat are often more interesting than jar foods. Appetite will vary day to day as growth slows a little. Avoid foods that need grinding until the molars come in. Toddlers often take on a yellow glow around the fingers, ears or toes. This is due to vitamin a from yellow veggies and will fade over time.