12C or 56F, think that's correct, is pretty chilly, but won't kill a Dieff as long as soil isn't kept continuously wet.

I'd cut off yellow/dead leaves. Also, let soil dry a between waterings.
Does the pot have drainage? If not, your Dieff needs to go into a container that does.

Feel the main trunk. Is it soft or firm? A healthy Dieff should have nice, firm trunk, otherwise the plant was over-watered to the point of rot.

Its leaves w/o yellow look healthy enough. You said the window was frosted. Do you have a non-frosted window? Dieffs need, at a minium, very bright light.

A word of caution. The sap is toxic. Be careful when working on a Dieff. Wear gloves or wash hands after handling. Toni

Well i took the plant outside today and had a look at the roots again in more detail. The plant was extremely rootbound and had little spots of mould all over them.

I cut this off and removed as much of the soil as possible and have repotted in some new compost i had (regular stuff with some john innes).

I have removed most of the bad leaves.

The stalks are very solid and not mushy. Have moved the plant to a brighter and warmer position to see if it recovers.

Is the soil muddy and does it have any kind of odor?

Steve

Steve,

No the soil in there was kind of a mossy soil. No apparent odour, but definately there were spots of mould on the roots when i took it out of the pot. Like you get on a loaf when it starts to go mouldy.

I've brought two of these back from death's door....one for a friend's wife, and one for my mom.
In both cases, I re-potted in a mix of bark, pumice, perlite, and a small fraction of potting soil.

In my experience, the leaves die as a result of root-loss...whether from rot or over-drying.


Josh

You didn't say if the pot had a drain hole or not. The plant has the look of one that has been badly over-watered or very recently over-fertilized. Your description of the 'mold' in the soil leaves me wondering too, if you might not have a case of root mealybug. Please do a Google Image search and take a look at some of the pictures of RMB symptoms that look like mold and see what you think.

I don't think compost is the answer insofar as an appropriates soil is concerned. That's sort of like out of the frying pan and into the fire. If you're decided on the soil you have, at least push a wick up through the drain hole to help drain any excess water too stubborn to drain on its own. You may also find some interesting tips on Dealing with Water-Retentive Soils if you follow the embedded link.

Your soil is a key issue, and the most important consideration when initially establishing a planting. Light or siting the plant is very important, but you can change that in a minute by moving the plant. If you need more help re soils, you can ask and I'll point you to some information I think you'll find valuable.

Al

I second Mealy Bugs. Google, or post a pic if possible.
Google, 'soil mealy bugs, pictures'. Several pictures with these horrible creatures will display. Compare to what you're calling mold. Toni

A frosted window in a bathroom is probably not providing enough light. I would move it to a better window. You have not provided your zone which would be helpful. Light is poor this time of the year and a frosted window is not providing enough light. Try giving it stronger light.

Jane

Have moved the plant now to a brighter location to see if it recovers.

The 'mould' was nothing like the mealy bugs mentioned.

Like i said it was 'mould' EXACTLY like a loaf of bread going mouldy - i.e. white dots with green centres.

Like seen here...

http://www.orchidgeeks.com/forum/attachments/orchid-pests-and-diseases/40117d1291003309-phal-repotted-now-has-mold-and-green-spots-img_0248.jpg

What is your plant potted in? Looks like bark. I think your house is too cold and the plant is probably overwatered. If you could get better photos, it would help.

Jane