I think your problem is over watering. They do not like wet soil - so water once or twice per week and lightly. Certainly let the soil dry out between waterings.

They also prefer indirect light - so sitting on a windowsill with direct sunlight all day is no good for them.

I would shift its location and water a lot less.

Is NSW too inclement for Dracena to grow outside?

I agree with Kildermorie - little water and avoid direct sunlight. It' also worth spraying for spider mites - they are invisible but can cause a lot of damage. Very often dreacena has got yellow leaves (suddenly) - most often because of overwatering - but when you keep it on dry side and have problems with spider mites that's the indication of their presence. Look up underneath the leaves and look for little punctures. Otherwise easy to maintain.

I'm only watering when the soil is dry which is recommended and not really using much at all. The soil is never saturated. I say often meaning consistently.. I'm not 'forgetting' to water it or anything :) The tree has thrived up until recently.
The leaves are a beautiful green but they're just drooping. They also have brown tips which is apparently a sign of low humidity. I've recently started spraying the leaves to help this.
The tree is also next to the window, not on the window sill. It's the window getting full sunlight. We have blinds so the plant itself is not in direct sun but does a fair bit.
There are no 'punctures' so I don't think there are mites.. Is it harmful to treat it for them anyway? Just in case?
I've added a photo to my profile which might help.
Thanks for the help anyway :)

Looking at the pic, I would cut off the top few CM of growth on the stems without any crowns of leaves. I would also re-pot the plant in a bigger pot with more compost and feed. Whilst doing that have a look at the roots to see if there are signs of rot (just in case it is over watering).

Cutting off the tops will stimulate growth within a few weeks.

Will do, thanks very much! :D

Hello! Going to disagree with everyone and say that your dragon plant lacks warmth, not direct light, and also lacks high humidity with damp, but not wet, soil at its base. John Innes No.2 mix with ericaceous will help. Direct full and dry light will put the plant under stress, as it will basically sweat. Do you have a warm window in your bathroom, or above your kitchen sink when you are washing up? Think jungle for this one!! A very warm, protected from winds etc spot in your garden, with a daily spritz of rain water is also possible.

The window it sits at is the warmest, it's the only window that's not blocked by the shade of trees apart from the kitchen window which the plant is far to big to sit at.. I agree with the lack of humidity which is why I have started to spray it.
I'm not sure if you're suggesting I'm stressing the plant or that I need to be.. The plant isn't getting direct light, the window is, it's effectively a dark but warm corner. I've added a daytime photo to give you an idea. It's taken around 10:30am and a very sunny day.

I will be buying new blinds over the next few weeks that should let in more light and probably a little more warmth. Do you think this will help? Or should I relocate once this happens?

I will repot the plant anyway because the pot looks too small for it and I'll cut the tips off too as was suggested to encourage the leaves to grow. :)

I would say you are not doing anything wrong. As you said the problem started as soon as you bought it... All dracaenas I was taking care of at work looked sad with drooping leaves after while... Repotting always helps, cutting off the tips should help too... But if I were you I would take it back to the nursery as soon as first signs of trouble appeared. And spraying for spider mites won't harm the plant.

Re-potted/replanted plants often if not always droop initially ... actually a good sign, meaning the leaves are withdrawing to support the new root structure, especially in a dry soil ... adding root builder to newly planted stuff is a good idea. I still believe re-potting of your plant in a 50/50 mix of john innes 2 plus ericaceous mix will rejuvenate this plant. I agree that after re-potting the tips should be cut back. However, just for info, I do have this plant growing outdoors against a south facing wall, and each year, with protective fleece, it keeps coming back!

Hi, thanks for all your help, everyone.
I had a good look at the plant and it definitely looks like the pot may have been far too small for it. The bulk of the roots were all clustered at the bottom of the pot where the soil was still pretty damp. All the stems that have lost their leaves have gone soft at the bottom. So definitely rotting. :(
Is there any way to save them if they've started rotting? They are all still lively and green at the top.