My advice is to let it recover. There's nothing you can do at the moment that won't cause more harm. Although you are losing culms, the fact that you have new growth is a very good sign. If you go mucking around, you're going to set it back more. I'm not sure where you got that other advice, but in my experience I have never known bamboo to get root rot or become susceptible to fungus as a result of a relatively short period of overwatering. My bamboo get drenched for months on end here in the rainy Pacific NW and have no problems...in the ground or in pots. Baby yours along and they will hopefully recover. It may be a year or two before you see significant new growth, but I'm optimistic.

I think you are over-analyzing at this point. Bamboo is tough and a couple of weeks of mistreatment should not affect it this severely. That's why I am wondering if the plants you got off of Craig's List might not have been badly divided and the die-off is a delayed result of the fact that they weren't as healthy as you thought. Can you please tell me what they looked like when they arrived? Specifically: How big were the plants? How big were the root balls? And how much dirt was on the roots when they arrived? Frankly, there are a lot of people selling bamboo online who don't know what they are doing, so it would be good if you could describe just what you started with, and what Zone you are in.

My boo seems to be getting moldy from all the rain we've had here lately.

You mean mold on the culms? Is it black, sort of sooty looking? I think it's not a problem and won't harm the plant, just makes it look dirty.

Thanks for your reply, very encouraging but I fear I still have some cause for concern. The largest culm has died along with 7 or 8 others.

It's not outdoors, instead in a container in my smallish apartment. Didn't get it from someone who often sells bamboo, rather from someone who had a couple plants and moved far away. He'd said he had them for 12 years or so.

While it was only a week or two of overwatering, it was sitting indoors in a container of stagnant water brewing the soil.

The drowned is the one that I didn't split. It was originally in a 15" inner diameter pot. Last spring I moved it to an 18" diameter pot and split the 12" one into the two pots. Rather inexpertly and during shooting. They all seemed quite happy until the incident.

I shook it to see if the leaves were loose on the dry ones (since even a couple months later the dried leaves are still green) and while the leaves mostly stayed on, it did have some sort of waxy looking white flakes coming off, but maybe that's just something that happens on dry culms? The healthy ones on the other plants didn't do that.

I've posted more detail and pictures here:

Here is a link that might be useful: http://www.bambooweb.info/bb/viewtopic.php?f=14&t=4906

coincidence-
I took a look at your photos and have a couple more thoughts. I didn't realize when I first replied that the bamboo was indoors. Given the low light level you appear to have in your apartment, and the plant size, it would be hard for the plant to sustain that amount of foliage. Bamboo can be grown indoors, but I think the combo of too little light and too much water contributed to its decline. And even if you wouldn't have had the watering incident, you likely would have lost a lot of leaves due to lack of adequate sun. I still think the plant will recover, but it is never going to look as bushy as it first did under those light conditions.

Also, it looks like the bamboo may have some slight pest problem, such as mealy bug or wax scale, so you should be giving it some soap and water spray until you quit having those white deposits and threads.

Thanks for further suggestions!

I'm pretty sure it stems from the overwatering as the other two plants of the same type are doing fine with no loss of leaves or culms.

The wax is present on both the dying and living, but only flaking off the dying one. I've seen no mealybugs. There are some wood lice but they're the type that don't roll up into a ball and from what I can gather that means they only eat dead parts of the plant. I've been operating on the assumption they're harmless if not beneficial so haven't made any attempts to eradicate.

Glad I haven't seen anything like wax scale, that would be pretty ick to have in my apt.

As for light, the window beside it is west-facing and one of my other plants is at a north facing window and doing fine with what is presumably less light from that direction. At least I THINK it's doing fine---I really am not an experienced gardener, quite the opposite. Do big plants like this take a while to be affected by suboptimal light and while it looks fine after a year perhaps next year or the year after it'll start dying just the same and all drowning did was speed up the inevitable?

Different bamboo species need different amounts of light...yours are probably ones that would prefer a lot of light. They should be able to survive in your apartment, but don't be surprised if they lose some of their foliage as they are unlikely to be able to sustain the bushiness I see in your photos. In 6-12 months compare what they look like with how they appear in your photos and you will likely see that they have pared themselves down because they can only support a lesser amount of foliage.