It's difficult to tell from the symptoms what the cause was, though environmental stress might be playing a role and its impacts sometimes closely mimic the symptoms of a leaf spot disease or insect damage. If the light levels haven't changed, have other conditions changed (such as a drop in humidity, common indoors this time of year), or has the plant been in the same potting mix for several years? Several species of tropical plants are sensitive to water quality and soil salts, for example, so regular repotting (perhaps every year or two) can help keep roots healthy and vigorous. Salts in this context are any mineral residues from tap water or leftover fertilizer that hasn't leached out of the potting mix.

Is the plant misted with water or sprayed with any other substance? If misted, such as with attempts to raise humidity, discontinue and try using a room humidifier instead, which works better and won't wet the leaves. Damp leaf surfaces can be easier for disease spores to infect. The spots pictured do resemble those of a bacterial or perhaps fungal infection (more so bacterial), but this would be hard to confirm from visual appearance alone. The only recourse in that situation would be to clip off the infected leaves to limit spore spread. Good air circulation and avoiding leaf wetness (which can also splash spores from one leaf to another) helps suppress disease indoors, though few (if any) fungicides are labeled for use inside, which limits your options for treatment.

As a general approach to keeping plant stress to a minimum, make sure to only water the pot when needed, feeling the soil at least an inch or two deep first to see how damp or dry the soil feels. When somewhat dry to the touch at that depth, you can water thoroughly, and if the pot sits atop a saucer to catch drips, empty the saucer promptly so extra water doesn't seep back into the drain holes and deprive roots of oxygen.

Overall, the plant appears to be in good condition, so this may just be a minor and temporary condition. If anything was sprayed on the foliage aside from plain water, this might be a phytotoxic reaction. Phytotoxicity is plant tissue damage from chemical exposure, and can occur from a variety of substances, like leaf shine sprays, rubbing alcohol, insecticidal soap (or a home remedy like dish soap), and even drifting mists from nearby spraying (such as window cleaner on any nearby glass). If any leaf spots have a phytotoxic cause, they will cease appearing once the exposure to the chemical in question ends. Diseases, in comparison, tend to spread or progressively kill more tissue in the leaf they first caused spots on. Insect pests can cause leaf spotting, but usually not in the style pictured here. You can check the undersides of the foliage with discoloration to look for mites, thrips, mealybugs, or scale. We don't see any clear evidence of their presence, but it won't hurt to check.

If this is a bacterial infection, it's hard to say where it came from if it hasn't bothered the plant in years past. Could snips used to trim the plant have been used on other plants in the home that might be infected, or on outdoor plants or produce in the kitchen? If so, disinfecting the blades before using them on the plant again may help avoid a repeat infection. Spores could come into a home through open windows, though usually pathogens find stressed plants easier to infect and overwhelm compared to those that are thriving and vigorous.

If the spotting persists into spring, you might be able to treat the plant with a fungicide once it goes outside. (If trying this, follow all label directions carefully, and consider testing a few leaves first to see if they develop phytotoxic damage within a few days after treatment before committing to spraying the entire plant. Few fungicides can suppress bacterial infections, with the active ingredient copper being one of them.) "Biofungicides" that contain beneficial microbes (often bacteria) that help kill or out-compete those that cause disease might be a gentler option, but they work best (when they work at all) when applied before a disease reaches outbreak levels and is causing lots of symptoms. These products also might not be labeled for indoor use, but you can check the instructions on the bottle to be certain.

Miri