I agree with most of the others - Different varieties of Hypoestes for the first two picks. Keep it pinched and trim or it will take over your tank in a not so pretty way! The dropped leaves may be the change in substrate. If #1 keeps looking bad just cut off the stems and sit them on top of the substrate (if the root ball is rotting this will get around it). If the stems are healthy they will root. If the root ball survives it will sprout new stems.
#3 is a varigated Columnea, and I'd probably say 'Broget Stavenger' is the likely suspect. 'Light Prince' has more lancolate leaves, 'Frosty Hills' can also get more lancolate and flush pink. As this plant grows out you'll probably be able to determine that better, as it could just be young.
#4 Yeah Selaginella... there are a bunch going around. I'm inclined to say along the lines of S. kraussiana because it's by far the most common, and it looks like that has the creeping habit of one of it's cultivars.
#5 I agree with Pteris ensiformis - a very pretty but weedy fern when it wants to be! Gets around 12-18" tall though. You've got a nice young one. I have had this pop up a few times just as spores that were in the substrate of plants I got (still sprouting 6+ years later!). Looks like one container is the plain green, another is the variegated one like yours LOL.
