Den. Dragon with yellowing and black leaves

[estación seca]

Agree with 1 Tbs/gallon is too much, but that's not the cause of the leaf problem.

[Dimples]

Originally Posted by Soccer10083

That’s what the bottle says to do, and it’s an orchid-specific fertilizer though.

While the bottle says 1 tablespoon, they may be expecting users to fertilize much less frequently than you are. Instructions on your average fertilizer product are typically aimed at non-plant-obsessed-hobbyists and often suggest a frequency of every 2 weeks or even just once a month because that's a "manageable" frequency for people that aren't highly hands-on with their plants.

They're also hoping you follow the recommendations and have to buy another bottle much sooner.

[Bamanana]

I had a Latouria type dendrobium with that exact leaf spotting. Someone identified it as a fungus. I am sorry to tell you that the only thing that got rid of it was a round of chemical fungicides, changing the type every two weeks. Apparently, some plants develop resistance to chemicals, so you have to use several. (What I was told.) But, having used three different chemicals (not brands, chemicals), one different one once every two weeks, solved the problem. The affected leaves were lost, but the plant was saved. I had a notion that it had to do with a horrible fungus gnat problem I was dealing with at that time. Several orchids were affected. Hope this helps.

[estación seca]

Call your agricultural extension office or the biology department of a university near you. They may be able to examine it under a microscope for you.