C. dowiana problem leave and spike
 

Last week i was excited as i see the first probally spike in my dowianas. But 3 days ago with the starting of the drop temperatures in the night i see a bit of black in the leave, and i start to put sulfur soluble.
Sudenly to night i see black in the what can be the point of the flower spike.
So supoussing are fungus i have used Fosetyl-Aluminium 30%.
Do you think is better cut the leave? is good the treatment i start?
Thanks in advanced

How low are the temps? And the plant gets direct sun?

Day temperature can reach in the day till 35, night above 20 , but yesterday was the first night got 18, probally some more days, but i didn´t really pay attention.

Now after summer 30% aluminium shade cloth.

How are you watering? They should not become dry when making new growth.

Are you using any calcium supplements? Prior to me using calcium nitrate as my primary nitrate source, I would see that very often with my cattleyas, the new growth would turn black, not from rot but not enough calcium (fert had no calcium). Now I have 5 new growths on an encyclia and 3 to four on my Catts and they are growing happy as can be. That's just my limited experience. Still haven't had anything to bloom on me yet, but most were obtained as seedlings.

Estacion Seca, i am watering everyday during the summer, over the leaves

Steve M , not about calcium, i have but i was afraid to used bcs didnt know how much ppm when using it, and after i forget.
So may you tell me please, when you use calcium, if you used alone or with boron? and anyway how many ppm you use?
I would like to used but would like to use safe,

Bout or you Thanks for answer

I enlarged the photos. You may have scale insects on your plant. Look up photos of this insect and compare them to your plant. If that is the problem, you need to treat quickly, because they can spread to other plants.

I use Calcium nitrate for my calcium and most my nitrate source. I also use KNO3 but not as much when I am seeing active growth but more in the fall. Im always adjusting my formulation and don't suggest this method, but I like to experiment. I use around 100 ppm Ca, but my water supply is very low in caco3. TDS of my water is 60 so its very low. But I make my own fertilizer with a few chemicals. It works for me but it is a good amount of work.

Estación seca, i hava a year battle with small snails, but didn´t find any other plague, any way i will do xtra check after your advise.

Stevem , thanks for your data , i used rain water collected in winter so i will try to adapt your numbers.

How often do you offer calcium to your plants.?

Your tap water may have calcium in it. Your water supplier will have an online water quality report for you to read. If you use rain water, you can probably mix some tap water with it to provide calcium. That is what I do. There is a lot of calcium and magnesium in my tap water.

You can buy fertilizers designed for use with rain water. They contain all the nutrients, plus calcium and magnesium. I have read here that people in the EU use Akerne Rain Mix fertilizer with rain water. It is easier than mixing the different chemicals. Perhaps somebody from the EU can enter the discussion and suggest where to get it, and how to mix it for orchids.