While I am no expert, I believe this is a fairly common thing with T. cacao. Usually the leaves turn brown from the tip going up, but I've seen leaves on my plants just like the ones in your picture.
Logee's has a video and they talk about this "leaf burn" at about time index 3:07.
If the burn occurs on old leaves and you see a new flush of leaves coming on, I would not sweat it.