My dieffenbachia sprouted several new baby leaves at once, at the same time the large mature leaves started dying. The new leaves never open or mature. Instead, they turn brown and remain curled in. Some continue to grow in size without every opening. Other plants in my office are thriving and had one with a bad infestation return from the dead but I can't seem to help the dieffenbachia.
Dieffenbachia New Leaves Die Before Opening
Certified GKH Gardening Expert
My top theory is that this is an insect infestation. More information on the insects that afflict diffenbachia can be found here:
Have you been fertilizing your plant? When leaves turn brown and curl like this, it could indicate too much fertilizer. And, how often do you water your plant? Is it possible you have been over-watering your plant?
Lastly, I would recommend a review of the care of diffenbachia at the following link: