Dying orchids

[Jancor]

Hi all!
I was trying to improve my orchids, but alas... I am out of ideas... Black spots appear on leaves, leaves become yellow and drop, new leaves are smaller (if appear at all)... What wrong with them? Over/under watering? Not enough air movement (I tried a fan - they did not like it)? Not enough food?
The first picture - all orchids together, 2-nd and 3-d - typical problems...
Thanks to all in advance...

[Leafmite]

What exactly is your set up? Temperatures, lighting, fertilizing, etc.

Without knowing your growing conditions, it is easy to misconstrue what evidence the picture shows. For instance, the healthy Phal with dark green leaves would hint at not enough light for the other plants. Yet, I also see Phals with pale leaves and some orchids with reddish leaves (indicating high light). This might mean that it is a temperature issue or, perhaps, a nutrient issue (your plants might need more Iron, Nitrogen, Magnesium and Calcium--a good dose of Ironite). The dark blotches on the leaves would suggest that a fan might actually be beneficial unless your temperatures are too cold.

[Bunch_Of_Roots]

This looks fungus. Get your hand on one of those computer fans and put that inside for air movement. And if your terrarium is fully enclosed, you should open it at at least once a day to let fresh air into the enclosure.

I see a lot of dew on the sides of your tank, which seems to indicate your humidity may be too high. When humidity is high, it is crucial to have air movement and fresh air.

---------- Post added at 10:26 AM ---------- Previous post was at 10:25 AM ----------

Also, cut the affected leaves, and then apply cinnamon powder on the fresh wounds.

[rbarata]

I see a lot of dew on the sides of your tank...

And in the second photo, one of the leaves has water covering it.
From what I see I'm tempted to think about too much humidity/low air circulation.

[Jancor]

Thanks for all replies!
Orchids were watering today in the morning (mist system, couple hours ago), do droplets are remains of this watering. The plants and walls will be dry in the evening.
I open the terrarium daily - the humidity is about 60%, temperature - 20-25C . I tried a fan - may be it was too big for my terrarium, orchids were worst. Should I try a smaller one?
About fertilizer - now I use only Orchid plant food mist. I tried to use what was recommended the seller of orchids, but after each fertilizing orchids became burned... I stopped to use it... I know that I have to feed them, but afraid to use this fertilizer (Dina Grow 7-9-5, used as recommended)... Now trying to choose a new one...

[rbarata]

I tried a fan - may be it was too big for my terrarium, orchids were worst. Should I try a smaller one?

A computer fan that's what usually people use.

[Jancor]

They are different in sizes - from 40 mm to 140 mm... I had (I think ) 120 mm. So what size is suitable for a terrarium 2' x 1.5' x 2'?

[rbarata]

Well, I really don't know. What you want is a light breeze and not a storm.

[3rdMaestro]

And have we ruled out the possibility of some kind of fungal/bacterial/viral outbreak? Orchids in close proximity to each other tend to share, but at the same time, I don't have much experience identifying sicknesses

[Jancor]

Originally Posted by 3rdMaestro

And have we ruled out the possibility of some kind of fungal/bacterial/viral outbreak? Orchids in close proximity to each other tend to share, but at the same time, I don't have much experience identifying sicknesses

And how can I do that? I checked several books, but pictures in them are not like my plants... At least, for me