the problem here is its dying roots
whats the indication of the appearance of the black ants?
how about these black spots?
im worried with its yellow green color
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the problem here is its dying roots
whats the indication of the appearance of the black ants?
how about these black spots?
im worried with its yellow green color
1st picture...could be black rot
See Orchid Diseases
2nd picture...ants may be drawn to sugary substance emitted by buds.
3rd pic...most likely a fungal infection
4th... High light leads to more yellowing...not an issue, I would think. Plants in high light need more nitrogen. How frequently are you fertilizing?

I agree with Ron or photo one could be snail and cockroach need to inspect them at night.

Great advice from Ron
Since you live in the tropics, I would get that cattleya out of that plastic pot and put it in a open wood basket with some large media or a terra cotta pot with some big chunks of some kind of media or mount it on wood or tree fern. The roots stay too wet and too hot in a black plastic pot in the tropics.
The vandas look like they have some kind of leaf spotting fungus. It usually doesn't kill the plant but it looks unsightly and the spots won't go away. Put the vandas where they will get good air movement and if you have a fungicide, use it twice (a week apart) and then once a month.
The light green/yellow color just means that the orchid is getting strong light. As long as the leaves don't burn, strong light is fine. If you move them to a slightly shadier spot they'll probably develop a darker green color.
