HELP!! Plants are yellow and dying from the bottom up.

My first idea was also that they look quite dry and underfed. Your plant is probably like: I need to salvage what i can from what i need least so i'm going to suck the last live out of the lowest leaves and deliver it to the flowers. (I would not have cut off the leaves that where yellowing but still had some nutrients and water in them as the plant could have taken from them still.) If you over watered then your roots might have been damaged and then you need to make sure that the top third of your pot stays quite dry so that the roots can take up oxygen there and you water from the bottom so that the deeper roots can take up the water from there. Roots need water and oxygen so that they can deliver it up the plant if either of those are missing the plant kinda dries out. And the shallower roots typically take up the oxygen as the higher earth typically is dry enough for that and the lower roots are typically in the ground level water. So some root mass can be totally submerged in water as long as there is also root mass that can breathe. So with that info you have to judge yourself if they where over watered or not. If not they look quite dry and you would want to water them with some more nutrients. And since you have low humidity to begin with you might want to put those pots in like some porcellan or something that would allow you to have 3-4 cm of standing water in like a bowl or plate. That way you can water from the bottom and have standing water at all times helping with humidity. BUT if you go with those bowls under your pots and they are constantly having 3-4 cm of standing water you cannot!!! water them from the top no more because then the top roots could not breathe no more and even though your plant has masses of water it would dry up as explained before.