That is most likely honeydew or nectar. But if the plant is very healthy, excess nectar is often produced. You typically find it excreted at the tip of an inflorescence, root tip and rarely a leaf tip.
But when you see it randomly on the underside of the leaf, that is spider mite damage. The nectar should not be there. False spider mites can be an issue and they typically do their damage on the bottom of leaves. Because they are so tiny, almost microscopic, they can inflict damage without ever being detected. Treatment is easy, dip a cotton ball or Q-tip in 70% Isopropyl alcohol and rub it under the entire leaf surface. Rinse with plain water. Repeat treatment a week to ten days later.
If it were mealybugs, you would see them.
