Sorry, I don't have an answer, but I have had this happen too. I ended up spraying with a fungicide, which seemed to stop the spotting. I will be watching to see what our experts say. It is so frustrating when something like this happens.

Oedema?

read up on oedema, seems to be connected with overwatering/rot.
all my sansi are watered sparingly, I did not water for a week after the repot - weather was in the 80s, but humid.
I misted couple of times, 'cause it's dusty here.
medium is at least 50% inert matter: like 1/3 commercial cactus mix, 1/3 orchid bark mix, 1/3 perlite. the new growth is clean, only older leaves have that. slowly I started giving more water. it runs out at the bottom fast. the larger plant was repotted 2 years ago in similar mix.
also eodema seems to involve 'watery blisters' which I don't have.
also may be it's sev diff problems?
most spots go thru the leaf. some are tiny and few and very red. one leaf (rightmost) is blackish spots (fungal?) , only one. the most common spots are transparent membrane that dried out with dark brown oval margin: see middle leaves above. one leaf (leftmost) has lots of tiny spots, I think they are growing - I want to trim it by half.
these plants are all in heavy clay pots, no glaze, only 2" of medium below roots - very shallow planting.
it's been dry - 50% humidity only and I have a fare amt of dust collecting - so I mist (very fine mist that dries almost instantly) on some days. not much, like once a week, but lately sometimes every day (based on low humidity).
in such dry conditions would fungal be spreading? so am inclined to think it's bacterial. I checked out fusarium - but I don't think its it.
treatment? I can't pull them out to spray: too heavy and too much work. the amt of leaves affected is not that much. can I just wipe with half peroxide or half alcohol or fungicide solution? or all on successive diff days?
I mean, i'll start these wipings today, it won't hurt. but can it help? anybody had stuff like that and was successful with treatment?

This is the info I was given:

"I think the first issue could easily be a residual symptom of oedema, which can result from over-watering at any point, but especially during periods of cool conditions and low light. An unscientific way to think about oedema is like this: The roots are pushing water upward. If the plant can't use all the water being sent, some of it causes cells to burst and die. During low light and cool temperatures, photosynthesis (uses water) and respiration are slowed, which compounds the problem to the degree that over-watering may not even be a necessary component for oedema to become an issue. "

It could be something else, obviously I'm not an expert. The frustrating thing about Sans leaves is that damage can take a couple weeks to show up after it occurs.

Could something strange have been splashed on the leaves?

no splashing - under the deep balcony overhang, no moisture except my misting (contains a little peroxide always).
no low temps -repotted in 80F, got even hotter since.
no overwatering, promise. I thought may be a little under-watering if anything.
and on 2 splits I barerooted, older medium is gone; all new fresh sterile and porous. but there might have been these spots before i repotted. i do have one plant that i have not touched - but it's the same spots.
i assume i won't find out what it is.
what's you thought on wiping instead of misting - my back just can't take pulling them out at the moment!

'cool dark house..' - sounds like 'cool dark lair..' - funny!
well, I trimmed the leaf with most spreading spots. and wiped with half water half rubbing alcohol.
tomorrow will do a fungicide wipe.
they are doing just fine otherwise, new growth is shooting, no more then 2-3 leaves affected in each pot.
I inspected my giant over 20yr old mama-sansi that remained indoors - no leaf spots.
so I pay with leaf spots for healthier growth outside.