We had the spots with dots we called them, not since our tanks where new. Appear to be clear egg sacks with little white eggs inside. Our guess was snail eggs?
They seemed to appear inline with one another as if being dropped off by a traveling snail.
Our tanks have hundreds of small (pea size would be bigger!) round snails, mostly come out of the rock at night.
A magnifying glass has always been one of the most fun accessories with our tanks, have a close up look~