This problem of browned leaves is affecting my curcuma as well as my globbas, even though they are in shade all day.

The plants are watered every two days, and are never allowed to dry out. They get a bit of organic fertiliser (sheep dung) and occasional serving of two-part liquid fertiliser. All the other plants in the same position e.g ferns, tacca etc seem to be thriving.

What is the likely cause?

Hope you can help,
Kind Regards
Mick