Not saying this is what you have, just throwing out reasons why I have the same problems, and what I do about them.

I have 3 things right now that are causing tiny black spots on my Hoyas:

-increased sun exposure (these don't wash off and are harmless)

-artillery fungus spores (caused by a wood decaying fungus, Sphaerobolus stellatus, (usually from dead/decaying trees or mulch), these do wash off and are completely harmless to living plants, although they can ruin your potting mix, if not kept in check.

-mechanical damage (old scars from puncture wounds; punctures were mostly caused by the aluminum ties I previously used to attach my plant labels- I now use wax thread).

I am not having any issues with wrinkly leaves, but when I have leaves that look dehydrated, I assume root or potting mix issues. I unpot and check the roots. If they look okay, I look at the mix. If it is getting old, I change it. At that time, I also check the old potting mix to see if it is retaining too much or too little moisture, and if so, I correct the issue.

If all looks okay with the roots and mix, I move on and ask myself these questions:

-Is the leaf an older leaf? If so, does new growth look okay? If new growth looks okay, I just pluck the older leaf off.

-Is new growth also affected? If so, is there a chance I have pests or that the plant is receiving too much or too little humidity?

As far as chlorotic spots go, the first thing I do is look at the underside of the leaf with chlorosis. If there is a crater or punctured area on the underside of the leaf that is in the same area as the chlorotic spot on top of the leaf, I just ignore the chlorotic spot, as it is most likely internal damage (bruise). If there is insect activity on the leaf underside, I treat accordingly.

Other than that, unless the chlorosis is accompanied by other symptoms (deformities in new growth, black spots that change in size, halo-ing (a halo of green, black, purple, or red-purple surrounds the area of chlorosis), dead or dying plant tissue, etc.), I just keep an eye out. Most of the time, if no other symptoms are present, the chlorosis gets no worse, and may even self-resolve.

Chlorosis can also be caused by over- and under-watering, water retention in the mix (poor drainage), too little sun/too much sun, cold drafts, excessive heat, fungal/viral/bacterial/pest problems, and too much/too little of certain nutrients.

Thanks so much aurorawa. I'll check to see if the mix is holding too much moisture. It has been hot and we've had quite a bit of rain and humidity. Those could all be factors and reasons why it seemed to come on suddenly. I'll keep an eye on them and I guess a little copper fungicide treatment couldn't hurt especially since they will be outside for another month. Thanks again.