The pot looks really small. Is it drying out too much for too long between watering?
Try this: Plunge the pot into a bucket of water and hold it down until it quits bubbling. Then let it sit for half an hour or so. Really saturate the soil. When you remove it the water will continue to drain away from the container, so be prepared. Then use a moisture meter or other test to see how long it takes to dry out to the right level of dryness. A good 'moisture meter' is a freshly sharpened pencil. Stick it in the soil about halfway down into the root mass. If the wood part of the sharpened pencil comes back dark, then it is still moist in there. Maybe wait another day or two and test again.
If the pencil comes back sort of spotty, then water.
If the pencil comes back dry (no color change) then you have waited too long.
If this is not the problem, then look into a few other ideas. Is the plant in an area where it gets air blown on it? Next to a heater or air conditioner? This can dry the leaves faster than the plant can pick up water.
