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This can be a few different issues. This occurs either because it has been over-watered. Has salt build up in the soil, or has been over-fertilized. This link will help:https://www.gardeningknowhow.com/plant-problems/environmental/what-causes-brown-edges-on-leaves-of-plant.htm

There are specific herbicides that will target broadleaves and leave your plants unharmed, but if you wanted to do this organically then you can pour boiling water ONLY on the plant, and right around its roots. This will kill it off.

Yes there are! This link will take you to a website with more information: https://www.epicgardening.com/cast-iron-plant/

This can be a few different things. The most common problem is root rot. This can be dealt with using wettable sulfur and dolomitic lime. This will kill most infections. For more vigorous infections, replacing 1/4 of your water with peroxide can help when you water. Can you include a photo? This can help me to see exactly what is going on.

Make sure that you only water when the top two inches of soil is almost completely dry. This will prevent future infections.

Split and damaged leaves may be caused by too much fertilizer. If leaves are starting to split, skip feeding for a month, then resume feeding with a diluted amount. You can cut off badly damaged leaves at the soil level.

I would normally advise to cut out the browned leaves, all the way down. But from the photo it appears that would be a big job and would mean 50% of the foliage.
Cutting the entire bed down is possible, and with good water management and fertilization, next spring and summer it will start to come back. But it may take a couple of years to recover completely.

https://www.gardeningknowhow.com/houseplants/cast-iron-plant/cast-iron-plants-information.htm

https://www.nola.com/homegarden/index.ssf/2015/12/whens_the_best_time_to_cut_bac.html