[Macanalista]

Discovered spots in lower leaves on three plants in one common pot growing indoors. Leaves end up dying, please see pictures

[deepwaterdude]

Hi, Mac, if you're in soil it looks like problems from either poor drainage or overwater, both resulting in pot staying too wet, rotting roots. If your medium is coco, you are probably lacking some perlite, rice hulls or some other neutral breathability agent, for lack of a better word. pH could be a problem in either case causing plant to not drink, keeping pot wet=same result.
Good luck, dwd

Edit: also, i see moisture on your leaves in the last pic. If you're watering and splashing the leaves, that could cause the spots, but leaves dying is due to something else.