That seems to be after-damage by bugs on 2last plants. You said one had mealy infestation, same for prevoius one (or perhaps different bugs). Bugs like to feed on very new growth, and crown gets damage like what you see: almost in a circle, since leaves are munched on while still tigth, young crown. If no more bugs (looks like they are all gone), it is cosmetic now and plants will just have to outgrow it - eventually, new leaves will replace old ones.

1st plant could also be some bugs - mites? - or fungal. It seems to me that 'attack' is over on that plant too, and it will have to outgrow it.

Those marks are all scabs, and will not rub off.

If the small black bugs also fly, they could be fungus gnats. In either case, clean up around plants (bugs like organic matter) and make sure there is no standing water (bugs often prefer wet environment). Good air circulation is very helpful. I hardly ever fertilize my succulents so can't help much with that - but plants that are (and often, or quite often) could get overfetilized. They could have a growth spur that could be attractive to bugs too (and tastier :). I am not saying yours are, just that it is possible.

Thanks Rina. I'll air the place more now. The bugs do not fly and I started growing chives and they seem to like it and that's when I first noticed them. I never seen them before with just succulents in the past. That may have been the suspect. Hmm.

All the previous bug invasion making me suspicious now hahaha. Anyway, thank you again.

Little black bugs could be aphids.

If ou have any outdoors space, put the plants outside.