Still new growth loss on Cattleya - Urgent call for input!

[Ray]

My gut keeps leading back to calcium, as I can think of no reason that an infection would only affect new growth tips.

[bethmarie]

I'm using General Organics brand CaMg+ 1-0-0, derived from calcium carbonate and magnesium nitrate.
Bottle suggests a teaspoon per gallon for light feeding, 2 tsp/gallon for heavy feeding.
I've used a teaspoon per gallon once, afterwards 1/2 teaspoon per gallon.

Also using DynaGro Orchid Pro 7-8-6, which recommends 1/2 tsp per gallon every watering-- I used 1/8 to 1/4 tsp at 3 out of 4 waterings.

The comment about the color of the leaves is something for me to think about, though I have several other catts blooming well under the same light.

[Leafmite]

I have noticed that some Cattleyas tend to be Calcium hogs while others do fine with nearly none. The other important things I have learned is to always plant the Cattleya on top so that just the roots go down into the medium and, if you water from the top, make certain that there is good air-flow to prevent water from sitting in the layers of the new growth. With a few of the orchids that tend to be more prone to water getting trapped in the new growths, I water from below and that has helped greatly.

Some members of the Cattleya family grow on limestone cliffs or in other Calcium rich spots where they get a steady supply of the mineral.

[estación seca]

I still think you might not be watering enough for your temperature and humidity.

[Sharon's Sheepdogs]

I also noticed a withered pb as estación seca mentioned. Are there enough healthy roots so that water uptake is adequate?

Some of the questions I have are:
1. What type of media is this orchid growing in?
2. What type of water do you use? Tap, Distilled, RO?
3. Do you check the pH of your fertilizer & CalMag before application?
4. Are you applying the CalMag with your regular fertilizer or separately?

It does appear to be a calcium deficiency so I wonder if the pH is too high or low or if there is something in your water that could be affecting the absorption of the calcium. If the pH is not optimal, some nutrients can be absorbed in excess or they can antagonize the uptake of certain other nutrients.

[bethmarie]

Originally Posted by estación seca

I still think you might not be watering enough for your temperature and humidity.

I probably can't argue with that, as I am the crown princess of being behind on watering. I do think the jury's out on whether there's another cause for the blackening of new growths.

[Ray]

Beth -

Looking back at this entire thread - but unfortunately without actually seeing the plant or experiencing the cultural parameters - I am at a loss.

I would likely rule out it being a nutritional issue, and if it was a disease, I'd expect it to affect the whole plant. That leads me to think the issue is cultural or environmental.