Hard to say. Usually, brown leaf tips mean brown root tips....and overwatering is one cause. Excess salts in the medium are another cause, as is bound roots. I would recommend that you re-pot the plant into a fast-draining mix to avoid root-rot in the future. Post pics for better advice.

Josh

It's true that it might also have an excess of salt, I noticed that the pot (terra cotta) was getting some white buildup around the bottom, which came off easily.

It currently is planted in a fast(ish)-draining mix. I don't have a specific recipe (not just yet), but I used mostly pine bark and gravel/stones (purchased from my local gardening store, so not like road gravel). I re-potted it into this maybe in late April, and it's been fine up until now.

I'll follow up with two more pictures, closer in on the leaves so you can tell more exactly the problem.

(sorry that the photo is rotated, the image uploading really could stand to be updated)

close up one, you can see some of the browning.

last picture. Oh! and before I forget, I made sure to check, but none of the trunks are soft, they're all nice and firm and healthy feeling, so I'm not sure it's gotten as bad as root rot yet.

Give the mix a good flushing, and then perhaps fertilize at full strength once a week (or whatever the directions on the package say). I wouldn't let it sit in the water...let it drain.

Josh