If in fact there are no insects to look to as the source, the next logical consideration would probably be 'guttation'.

Al

Yeah, Probably just guttation. Some plants do that. Philos do it a lot. If the "water drops" are a little sticky when rubbed on your hand it's a good bet. Usually clear but it can be tinted.

Read the link below

Here is a link that might be useful: Guttation explained

Aside from the plant itself exuding moisture from the leaves one should keep a vigil to see if indeed a bug is hidng.
You're right in assuming a possible infestation of scale insects or mealybugs--both produce honeydew and can be detected sometimes by the shininess of leaves. The scale insects are hard to see on fronds because they resemble spores.
Nonetheless, plants can be given a mild solution of lime sulfur or dormant oil. Because the scale insect has a hard oyster shell-like body you can add to the solution a measure of rubbing alcohol which can eat through the shell.