A different Hibiscus, same problem but more advanced.

IvoryCirce, looks like mite activity.
one of many Links.

Doubt it's erinose mite. "Spots"/marks are quite different.

Looks like the plants are indoors. What fertilizer do you use and how often?

Thank you both for the replies, I appreciate it so much.
I won't rule out mites but I've scoured every inch of the effected leaves, even pulled out my magnifying glass and can't see a thing on them. I've showered them off rigorously, I haven't tried spraying for pests yet but I will be trying that next to rule it out completely!
I haven't had a run in with the erinose mite before but if it makes actual bumps then I don't think that's what this is, the marks on them are little specks rather than spots or bumps, it's like the cell in the leaf has broken down and I can see through it.

My Hibiscus are potted, but were outdoors until I brought them in a few weeks ago for Winter, they started showing this problem before I brought them in. Not all of them have it, only three or four out of thirty or so, and they're all treated the same.
I use the fertilizer from HVH once a week: Fertilizer

Your opinions mean a lot! Thank you. I'll keep trying things and see if I can figure anything out.. Hopefully it's just some little mite that I can't spot.

What was the lowest temperature before you brought it in?

And please do post an image of the entire plant.

IvoryCirce, OK. Try This Image.

IvoryCirce, and here is a more detailed description.

The images of the virused leaves don't match the OP's image.

IvoryCirce, it was 1965; and a supervisor / mentor of mine and I were looking at a leaf to determine whether it showed the symptoms of a bacterial disease.
"It does not match the pictures in the report", I opined; trying to sound intelligent and confident.
"The bacterium did not read the report", was his laconic comment.
Plant diagnosis is essentially a process of elimination.
You seemed to have taken the right steps to uncover insect pests; to the extent that they can be eliminated.
There remain diseases, cultural and environmental considerations.
The leaf "spotting" suggests something internal - a disease or a nutritional disorder.
The fertilizing program appears to be adequate; but it could be inadequate, or at the luxury level.
I cannot say that I have seen them all, but I venture to say that the leaf symptom does not indicate that nutrition is the issue.
I would look at diseases next .
You sound as though you will enjoy the article at the link below. It focuses on turf but can be applied to all plants.
It has been if invaluable assistance to me over the years.
LINK.

You aren't using any sort of ozone generator are you?