Any idea what's going on here? Multiple genera

[Pynn]

Leaf spotting/discoloration like this is showing up on a couple of my orchids - this one is Bulb tingabarinum, but it's also happening to my Milt's and Den's. At first I thought it was just a watering issue - but now I'm scared a recent addition to my collection may have been diseased. Any ideas? Thanks so much for input!

[SouthPark]

If the leaves aren't degrading due to old-age, then possibly a fungal infection and/or bacterial infection.

Maintain nice growing temperature for the orchids, and provide gentle air-movement in the growing area. And keep the leaves dry.

And for now - if you have some - could apply a systematic fungicide - such as monterey garden phos. Or maybe a copper spray (orchid-safe one) ----- spraying leaves - underneath and over the leaves and stem.

And put the plant in a medium light area --- no direct sunlight for now.

[estación seca]

Need more information - light - window? natural? electric? watering? temperatures? humidity? fertilizing? growing space type - greenhouse? room? light stand? terrarium?

What are the other plants you're having trouble with? There are thousands of Dendrobiums from many different climates.

[Ray]

Looks like a systemic infection to me - a well-advanced one.

Sorry, but in my book, that's a pitch and replace situation.

[SouthPark]

Pynn ----- there's definitely some urgency with this case for sure. Do you have systematic treatments like monterey garden phos and/or copper spray?

I forgot to mention - those badly affected leaves will not make it anymore. Use a sterile and sharp cutting tool to remove those badly affected leaves. And clean the tool after that - sterilise it.

And spray systematic fungicide on all parts of the remaining good leaves and stem, then make sure to provide gentle air movement in the growing area.

[JScott]

How are the roots? Did you tap the plants out of the pot and check on the root health?

[Pynn]

Roots look good. I have neem oil I can use. These plants are in a 80-90 degree grow room under medium to bright LED light with one circulating fan. Humidity normally hovers around 60%.

I'm gonna cut the leaves, apply fungicide, add some more air movement, and try to bring temperatures down. Thanks for the all the valuable input everyone!

[SouthPark]

pynn - I think the neem oil is for dealing with insects. So probably don't need to use neem oil here.

That's great how you have a circulating fan already.

Regarding the medium to bright LED light ----- I recall there was a case where a member had the lights too close to one leaf - resulting in the leaf temperature too high, or the leaf not being able to get rid of the heat fast enough.

This won't necessarily be the issue here though (with lights). But just mentioning it - in case it helps. Had those orchids been growing under those same lights for a long time? If so - then it's probably not the lights being the issue.