purple patches
 

hello!
i´m having problems with some dendrobiums. almost 6 months ago some of the leaves of a dendrobium i have became purple but not all the leaves; after that the orchid hadn´t had new growth. i have another dendrobium with the same problem but this one it´s growing quite well and the new leaves doesn´t have that problem.
i was thinking it can be caused by sunlight but now i´m not sure.
picture 1 and 2 is the one that it´s not growing and picture 3 is the one that has new leaves.
hoping to have some answers with solutions
thanks a lot!

Its most likely just from high light. It means you are growing it at good and bright! I would just keep it as it is.

I agree, it looks like a reaction to stronger light than the plant accustomed to.

I would agree with those above, this seems like you are growing in the "higher end" of its light preferences- as long as it isn't getting burned, you should be fine!

yes mi city is warm all the year, thanks a lot!!

I had this once and to see if it was a high-light level issue, I placed a small piece of black electrical tape on one of the leaves, turned the leaf so that it was in the strongest sun and waited two days. Sure enough the leaf turned purple, except under the tape. It was a light exposure that brought it out.

should I put the tape on a green leaf or one that is already purple?? not all the leaves of that orchid are purple

No, the color of your plant is very good. It is healthy the way it is.

When I have used tape, I put it on the green leaves; if they turn purple due to light, it will not show under the tape. Just an old trick I picked up years ago with other plants. It may take more than a couple of days, but once the green leaves start to turn purple, take the tape off to be sure it is a result of light.