Are there any roots trying to grow out the drainage holes? If so, a transplant is in order.
Only go up a planter size or two, not mega planter. It's not thirsty? Good luck, Oslo.
you can not tell with the bars and discoloration
here is a nice photo trick.
take a pic using the flash alone when the lights are off.
but I will send you this it is a pretty good place for plant problems Web Gallery Wizard™