Lack of light, too much dust, or not enough water are only a few issues that can plague indoor plants.
Here are three small steps you can take to get them back in shape.
Grate the soil
With a small hand cultivator, you can grate the first few inches of the soil’s surface. Try this especially for larger pots.
The idea is to move the soil around enough and reinvigorate it, as well as remove any lingering dry crust.
Be careful not to damage the roots, which are soft in fragile in many cases (e.g. clivia plants).
If the water you use for your plants is calcareous, it’s possible that a whitish crust has formed on the surface. You’ll need to remove it first.
Take this opportunity to add a mineral and organic mulch around the plants, which keeps them healthy.
Use a sponge with deionized water to wash the large shiny leaves.
Never use a polishing product.
The priority is always the upper leaves, as they will have the most amount of dirt and dust.
Rinse the sponge every other leaf at least. You don’t want to wash with a dirty sponge, as it would help the dust penetrate even deeper.
You can also shower the plant with lukewarm water, which is usually a good idea for indoor plants.
Cut withering stems
When a plant has little to no light, it produces thinner internodes that elongate between leaves. These newly formed leaves are smaller than others.
Shorten these stems, and taper them to a level where the leaves appear “normal” (or at least are large enough).
Indoor vines (cissus, scindapsus, etc.) are quite sensitive to this phenomenon.
If your plant regularly develops these thinner stems, it may require additional light. Consider moving it closer to a window.