Oh my, I'm sorry, I'm posting again on your post, I edited my post and forgot to add the picture again. >.

Where are your plants during the day? Inside or outside? What kind of light is it getting?

Mine is outdoors, getting indirect sunlight a couple hours a day (mainly morning sun, perhaps an hour in the afternoon at the most).

Something just occurred to me... it's behind a glass table, is it possible that sunlight that's hitting the glass table during the morning is going through the table and hitting the leaves (just a random thought)?

Planto

It doesn't look harmful to me, but then again I'm just a newbie.

I thought I read that hoya can get spots on their leaves from chills. I don't actually know what it would look like though. Sometimes Gardino's nursery sells hoya which have 'spots on the leaves,' and they continue to say 'will not affect the health of the plant, if your growing conditions are different the spots wont continue. Only purchase if you understand!' Haha. I've always wondered what kind of growing conditions were causing those spots and what was needed to cure them. In any case, I'd try doing a search through history while we wait for the pros!

Keiko

We recently had a thread on this very topic.

http://forums.gardenweb.com/forums/load/hoya/msg070656198793.html

The pigments that are responsible for red, purple, or blue in plants are called anthocyanins. This is not a disease, only a response to light levels.
Please read the info in the wikipedia link below.

This study is much more useful if you want to understand the response you are seeing in your Hoya. The roles of light and temperature are explained here while they are not in the wikipedia article.

https://sharepoint.cahnrs.wsu.edu/blogs/urbanhort/Media/PandP%20review.pdf

Mike

Here is a link that might be useful: Anthocyanin

Mike,
Thanks again.

Planto

Mike, thank you for the link to the Anthocyanins article. After reading it, I think the best explanation would be the two nights of relatively cold temps we just had here - 54 and 53. I thought my baby would be sheltered enough on my covered porch, but I assume this is a hint that she'd prefer to be inside on those cold nights.

I'm glad it's not critters, and consider it a lesson learned: if I'd be too cold, so will my hoyas!

OMB - The very same thing happened to my pubicalyx last year when I moved my hoyas into the house for the winter... The night I brought them in I just happened to check the weather for the next day and saw that the current temp outside was 28 degrees fahrenheit, which RARELY ever happens in my area, so I had to high tail it outside at 11:30 at night to bring all the hoyas into the house. Within a day or two I noticed the spots on the underside of the leaves on my pubicalyx and my rubra so I'm guessing that you're probably right about the culprit being the temperature drop you had recently based on my experience with this, and also the fact that your hoya's lighting situation did not change over those two cold nights you just had. A few days after returning my hoyas to their outdoor home last spring, the spots began to go away. The spots are all gone now so I'm sure yours will go back to normal in time :) I'm going to test my theory this winter though, and bring my hoyas inside way before it starts getting cold at night, so we will see if it happens again that it may actually be lighting as well, since where I keep them during the winter is not very brightly lit during the day...

Mike - I'm going to head over and check that article out now it sounds very interesting ;)

I ordered one of Gardino's plants with the spots on the leaves and it is robustly growing with the new leaves looking fine.

Susan

I have those spots on my plants, and we definitely haven't had any nights below 70F. I've always considered them to be the notice the plant is receiving the maximum sunlight - kind of like a suntan.

Renee