I agree with the first poster-you are watering too much. Also, these plants will naturally lose leaves from the bottom of the growth as the plant grows, so you should never have to prune top growth. I have a number of these that are about 25 years old. They're on two covered porches and both have gotten the white "stuff" you mention in the top cupped section of the leaves. It is a type of scale, which is a sucking pest. Take the plant to someplace where you can spray it (outdoors or a tiled kitchen floor because you'll create a mess). Use horticultural oil spray & make sure to coat the tops & underneath portions of each leaf and the trunk. It will coat the scale & should kill it. After the scale is dead, you can wash the plant with a very mild soap/water solution. Rinse it well and rinse the soil through very well. Then let it dry out before you water again. If the new growth does not form at the top, you can do what the first poster suggested and cut the tops right off. If the trunks are still alive, they will sprout at least one shoot just below where you cut. If you do cut them, cut them at staggered heights for best appearance. In the future, to propagate these, cut the tops off of any too-tall or ungainly stalks at the height you want the new shoots to appear. Let the cut pieces "harden" a little while & then push them into the dirt. They should root over time!

The first thing is to get the watering right. Buy a water meter at your local hardware store. It shouldn't cost more than $15. Mine came with instructions about when to water what plants. Overwatering can kill plants as fast as underwatering and some people start watering more when their plants look sick, compounding an overwatering problem.

Next, wipe off the white stuff. It might be bugs, it might be mildew. It's certainly not doing your plant any good.

Lastly, that pot looks small for the size of your plant. Consider repotting. It's better to do it after the plant looks healthier, with the caveat if your problems are caused by sog, repotting into something dryer will help.

You could have a virus or other difficult to cure disease. It's possible, but without knowing more, I wouldn't put much money on that possibility.

I would also consider a larger pot. It's hard to tell from the photo but the plant looks much too large now for the pot it's in.

That plant is gone.

These guys are hard to kill but you seem to be managing just fine ;-) you are waaaay overwatering and that poor thing needs a pot over double that in size. These are plants that don't want soggy bottoms and are similar to yucca (a desert plant!). Let it dry out a it between watering and mix a bit of sand in the soil when you repot. It won't hold moisture as much.

Another thought: it looks like you may have just recently purchased this plant, based on the taping & blocking. The scale may have already been on the plant when you bought it. You might be able to return it. I know Home Depot will take their plants back within the first year (I think).

Thanks all for the comments!!! OK so my main takeaway is to stop over watering. Message received! I intend to revive this plant because I have killed others before it and I'm trying to make up for those lost plant souls. I suppose diagnosis is my next step so I can be sure how to treat. I took a closer look and found a few little things that may resemble mealy bugs although they weren't moving and I'm no expert. I took a couple more closeup shots - can anyone confirm? Regardless can I still use a horticultural spray to treat these? And on a side note, when is it time to remove the tape and blocking? I bought the plant a couple months ago and was told to keep that on until the plant was sturdy. How do I know when that is?

http://www.gardeningknowhow.com/houseplants/hpgen/powdery-mildew-treatment.htm

I wish I could tell you definitively what you have there, but it could be mealybugs, aphids, cottony cushion scale or a fungus. I think it's likely an insect pest. Horticultural oil will help control all of those. You can also mix a mild soap solution (NOT Dawn or heavy grease cutting type; those are too strong) and mix that with the oil. Both of these products are non-toxic. I have "cured" mine with oil spray followed by a thorough washing with mild soap & fairly high-pressure rinse with water. I still recommend you contact the seller & see if he'll exchange it for you.

Some more info: GreenMethods.com › scale-mealybugs