As a commercial interior horticulturist, I have often cared for cast iron plants (Aspidistra), as well as their fellow low-light plant, the snake plant (Sanseveria). No the plants are not related, and the light you describe does not sound really low, but bear with me a moment, you might be able to use something here. The first thing I noticed about them is that they - more specifically their roots - can be damaged by not aerating sufficiently between waterings, but the damage doesn't show up for weeks or months. Correspondingly, one may make adjustments when problems are noticed, but not see improvements for weeks or months. The second thing I noticed is that the moisture/aeration level IN THE VERY BOTTOM OF THE POT is what you need to be aware of, not just a couple of inches down. Before watering, use a probe to investigate that moisture, pushing your probe all the way to the bottom. For low light, the probe should feel completely dry; for low moderate light, there should be only the slightest trace of moisture. If the soil has not reached that level, DON'T WATER. Test again in a few days, or even a week, and don't water until that aeration level is reached. When you water, water enough that you get a run off from the drainage hole, 1/4" will be sufficient. Let it sit for a day, and if there's any water still in the saucer, you can dump it out. I'm making the assumption that you're using some kind of conventional potting soil or soilless mix, not a coarse potting medium like "gritty mix" or 5-1-1. I can't talk with much confidence about those, as I'm just beginning to experiment with them myself. As to whether you should repot now, trimming off damaged roots, doing general root pruning, and using an improved draining mix, or try to improve the health of the roots (leaching the soil was a good first step) by letting them aerate more first, allowing them to regrow, then repot in maybe a year - that's your choice. Some people will advise the former, some the latter. Doing something drastic to an ailing plant is sometimes not a good idea, however. I would recommend that when you do repot, try a coarse, quick draining mix - I think your Grandma would have been very interested.

August/September before dying in fall.

Wean the plants off of the high humidity. Open the cover on the bin to reduce the humidity. Do this gradually over a few days to acclimate the plants to lower humidity. Closely observe the plants during this period. If they start looking bad; add more cover. When the plants have healthy leaves and a cup full of roots; then repot

I'm going to tee off on sushipup's suggestion. From almost two decades caring for mom and dad until their passing, I have very strong opinions about papers and directives. If/when an "event" occurs, you won't know what it will be, how it's going to go, or if you, yourself, will be thinking straight or not at that moment. Carry (on your person!) THREE copies (separate packets!) of POA, living will, DNR, Medical POA, current medication list with dosage and schedule, Medic-Alert sheet describing known existing conditions. One set for you, one for EMT's, and one for the hospital. Takes little space and can save time, confusion, and aggravation at what may well be a critical time. In my personal experience with (many) instances of necessity, having these documents ready to hand over to EMT's and hospital staff saved MUCH time and confusion for everyone....and allowed ME to worry about other stuff. On every single occasion, I received feedback from EMT's and/or hospital staff along the lines of "This is great. I wish everyone did this."