Close up views can be helpful in determining what's wrong but, here, it's challenging to know how this view related to the whole.

Please post a picture of the entire plant/planting.

If that's not possible, my guesses are too little light, possibly too much water.

Or possibly too few roots to stabilize the plant.

Please post an image of the entire plant where it is sitting/growing. Doing so will help us provide more specific info.