My Cochleanthes in bloom and diseased
 

Repot it soon after I got it...this is the 2nd blooming under my care...however it has this issue which I think it's bacterial...leaves start to get yellow and 3 to 4 days later they fall. This seems to be happening only on older growths.
I also found that there was an ants nest in the pot...drown them all, obviously (but it was interesting to watch them trying to save all the larvae by climbing to the tip of the leaves, holding them in the fangs).

Anyway, I tried to see the reaction to an anti-fungal treatment but so far, no good.
But the plant is growing new roots.

Here's some photos with an advise request about available treatments in Europe.

https://i.postimg.cc/LqRLGHms/20200802-200742.jpg

https://i.postimg.cc/6T1VTJfH/20200802-200756.jpg

https://i.postimg.cc/svkp9Y87/20200802-200814.jpg

https://i.postimg.cc/LnYt1Cym/20200802-200910.jpg

https://i.postimg.cc/6TQL95n2/20200802-200924.jpg

https://i.postimg.cc/gx33MwF5/20200802-201016.jpg

https://i.postimg.cc/LqBBsJxf/20200802-201024.jpg

I seem to recall most of these don't want hot temperatures, and don't want direct sun. And they don't like to dry out, ever.

This one is indoors where temp reaches approx. 29°C max in this time of the year. RH might be too low, around 30% max.
Light is bright without sun all day (north faced window).
The medium is highly water retentive: small/medium size bark + perlite + coco chips + LECA + 40% sphagnum.
Considering the look of the leaves, do you think it's environmental?

It has the look of environmental problems. It looks like it can't take up enough water.

I have been watering 1x week. The medium is higly water retentive and it's overpotted. I think I'll repot it into a smaller pot after the blooming is done.

if the RH is too low it might not be breathing at night...can you up the RH a few nights and see if it helps? maybe bring it to the bathroom and take a shower before bed LOL, you know, for the orchid

I can put it outside... temps around 17°C and RH > 80%.
I'll give it a try!

given what ES said and the conditions you describe inside, i would try it.....do you have a similar lit spot outside?

Yes, same window but on the outside. I will put it out only at night. During the day it would not last a week... too hot!

i hope that is the sweet spot...Thanks to ES and Ray, i have learned so much more about the day/night uses of the plant as far as respiration and thus total digestion/resource management. just switching to watering my Tillys at night has been like a switch was turned on in the plants....

I hope this works as well for this one

I water some of my plants at night when temps go down exactly because of that. My rupiculous, for ex, as well as my anceps and tenebrosa are always watered in the early evening when temps go down and RH goes up.
One of these days I'll find a way to increase CO2 % to make it even better.:)

welding companies and paintball places can both sell/rent cylinders...….if you REALLY wanted to :evil:

Well, I can't do it at home...the results may be catastrophic. Good for orchids but not good for me and my family.

Adding CO2 to night-respiring plants doesn't help. They take in CO2 and use it to form a 4-carbon organic acid. As this happens the pH of the plant drops. When it reaches a certain point the enzymes stop working. In cacti, most have absorbed all the CO2 they can before midnight.

The next morning they use the sunlight to combine the CO2 with water. The pH rises as the acid is used up. Their pores are closed so sugar production is limited by how much they absorbed the night before. Cacti are done working for the day by about 10 am.

I've been told people can taste the difference in pH during this cycle.