That leaf looks quite concave, like the Colocasia 'Tea Cups'. It also has the dark petioles and leaf blades. They rarely produce seed though, but propagate by runners.

Hi & welcome! These plants look absolutely gorgeous together! I'm not sure they're the most practical partners. The blooming ones (Mandevilla & Geranium/Pelargonium?) prefer much more sun than the others but if they keep blooming, they're not bothered by it. If the sun isn't too intense and not shining right on the pot during the hot part of the middle of the day, the other plants might not mind too much. Is there some sunburn on some of the Ti plant leaves? Spider mites LOVE Colocasias. Do you see any spider webbing on the back of leaves? Does your pot have a drain hole in the bottom for excess water to escape?

Looks like older leaves dying off. No biggie. However, these plants don't typically carry a lot of leaves per stem to begin with ... particularly when grown indoors. They like it hot and bright. Avoid direct, hot afternoon sun.

"Special attention" is a pretty subjective term. For instance, full repots that include bare-rooting, root pruning, and a complete change of soil on a regular basis is not "special attention" to me. It's simply a regular part of the program by which I'm able to keep perennials alive (trees are perennials, too) and in a high state of vitality indefinitely. Most growers are not even aware that this is the only way to avoid a steady decline and eventual death of the plant due to the effects of root congestion. This is definitely a cultural consideration that can cause problems that lead to the plant's demise. When it comes to container media, your focus would best be directed to your medium's structure, not it's ability to feed the plant. Trying to build media that are able to feed the plant is fraught with tribulation, because the hydrocarbon chains that organic materials are made of must be broken down to reduce then into elemental or otherwise usable (to the plant) forms. This destroys the soil's ability to hold a favorable ratio of air:water, which results in poor root function/health. Much wiser for the grower to work at ensuring the soil is able to retain its structure for the expected interval between repots, and shoulder the entire burden of providing nutrition. If you aren't fertilizing, you're overlooking a responsibility that belongs to all container gardeners. Lacking adequate nutrition, plants 'steal' any mobile nutrients from other plant parts and use those nutrients to fuel new growth while shedding old growth. This is not a sustainable arrangement and always ends in death of the organism unless the trend is reversed. No organism can use more energy than it can produce for long. You might find information that provides additional insight if you follow the link. Plants require conditions they can tolerate. If they can't, it leads to stress. Stress turns to strain, and the inability to make more food than it is converting to energy and using. This means the plant cannot grow. Growth isn't measured by how many new leaves a plant might produce, it's measured by the increase in dry mass; so, a plant that is putting on new growth while shedding old parts isn't necessarily growing, and plants that aren't growing are dying. I guess the main point I would make is, there's a lot more to growing things efficaciously than bringing them home from the store and watering them when they need it or we get around to it. I look at it from a scientific perspective, and I shun trial and error. Knowledge about soils and how plants work (physiologically) is the propellant by which you can most rapidly advance. Trial and error, essentially stumbling around in the dark is more a tether to bad habits than a method of learning. That's just one person's POV. YMMV Al