Inadequate soil volume (insert pot is too small for the size of the plant), water issues (too little, or if the outer pot does not have drainage, then the inner pot may be sittinging in water and causing root rot) nutrient deficiencies, pest infestation (possible caterpillars).
Re-pot into larger container with good drainage. Avoid an outer pot that doesn't let you monitor and avoid standing water. Use a nutrient rich organic potting soil and fertilize with a mineralized complete organic fertilizer.
Water appropriately. Pest problems should minimize when you get the soil and water management right. Consider preventive applications with 70% neem oil.