Something is happening to our Orchids!

[InsanityShard]

Something strange is happening to our Orchids. They lose their leaves, usually one at a time, they turn yellow, then black. It's even effecting the latest Stanhopia flowers. It doens't matter if they're inside or out. We have a pretty bad drought here. Even the baby leaves are dying on one of my indoor orchids, which are in cooler temps with a drier atmosphere, even though I keep them on top of a fish tank. It doesn't seem to matter how much or little we water them, and it's not the heat. It's not just us either, at least one other person we know grows Orchids and they;re having the same issue, despite being in town, a fair few kilometers away from us. We're in South East Queensland, along the coast. The strangest thing is when they turn yellow, then black, it spreads from the side of the leaf, just one side, not the middle, and spreads from there. Not even from the stem but the side. We currently have freshwater slime mould in our tap water, could this be having an effect? I'm sorry I can't post pictures. My camera won't connect to my computer. It's also on one of those thick bud things the leaves come off on one of my orchids. My mum has dozens of orchids and they all seem affected, except the batflowers.
When they turn black they're not shrivelled, they stay thick with water inside, but a bit softer, but not like they have too much, in fact it seems they have a bit less but they don't shrivel up until after they fall off.

 

[InsanityShard]

Mum reckons it's the weather but I think it's the water. Aside from the freshwater slime mould in it, the orchids that get watered less aren't affected as badly, I've noticed today.

 

[Becky]

Sounds like it might be overwatering. What are the roots like?

 

[InsanityShard]

It's not, all the roots have been very dry. It's not anywhere near as humid as usual with this drought, but we haven't been watering more. Even mine are sufffering this, and they get watered about twice a month. While less water seems to help, it still happens, even when you let their bulb parts shrivel up like prunes.