I haven't grown caladiums, but I am growing elephant ears (colocasia) and alocasia, which are close relatives. I grow them in large wooden tubs in the summer. They are in an area that is fairly shady most of the day. I have found that they want much more water than any of the many other plants I've grown in decades. I have to water every other day even though the surface of the soil is still moist. Otherwise they wilt dramatically. I added extra peat and composted manure to my standard 5-1-1 this year, and the plants are thriving. I think your caladiums need more water, not less. They may also need larger pots. I can see roots near the surface of the soil in my 20-gallon pot on a plant that was nothing but a tuber two months ago.

I haven't had that problem with my titanum but my gigas (which is pretty similar to titanum) had all sorts of problems over the years. One season a tree branch fell on it and broke the petiole. Insects got in and ate out the inside of the petiole. The plant went into early dormancy, it had only been growing for a couple of months. Gigas grows for one year and then goes dormant for one year. But afterwards it came out of dormancy earlier than one year and grew okay. Another season I had put it into a more exposed position and it got badly sun burned. It went into early dormancy that year also. Last season it was broken by the wind. But I found it very soon after, tied it up and painted over the damaged area of the petiole with grafting paint. It kept going for the rest of the season without going into early dormancy. When I saw it damaged the first time I went into a state of shock thinking it was going to die. But now, after a few dramas, I don't worry so much and just do what's needed to keep it going. So hopefully there won't be any more problems but if there are I feel fairly confident of being able to successfully deal with them.

That's what happens when dahlias don't get dug each year or two at the most-- a big mess that's hard to divide. Go to the post on splitting dahlia tubers posted by jroot last April to see how to divide them. When all else fails & to get started, you can just whack the clump in half or quarters & start cutting out the rotten ones- just be sure you don't cut the eye parts off of the individual tubers. The mush means those tubers are goners but some of the lower ones might be OK. The rot will spread if you don't get rid of it.

Mel-grower, Thanks for rephrasing the question, as it is a good one. While potatoes have eyes sporadically all over the potatoe, dahlias have eyes only on the collar. I have split the tuber as you suggest with a piece of the tuber, and a bit of the collar containing an eye. The problem that often occurs is that rot sets in, hence I try to minimize the cut on the tuber. That being said, I have had some success doing it the way you describe. Sometimes, I have found the tubers to be too huge, and have cut off the bottom part. When I cut, I always add some bulb dust/fungicide to help cure the cut, and prevent rot. I usually start them in the medium first, so that I can clearly see where the eyes are, and then make the cut. We all learn through experimentation. Try some, and let us know how it works for you. John