Hello, I recently was gifted a Bonsai growkit and instead of getting straight in I tried to find information on the tree I had, and failed.
Maybe someone could give me some identification?
Also, all of these trees are from one pack of seeds, I had to divide them as I didn't know if the roots would kill the other trees, and I'd hate to see them fail. The three of eight I repotted grew quite quickly and seemed to be doing well except having a more yellow-ish colour to it - however, they soon died after a few weeks which made me think maybe I under/over watered?

Pics below, shine some light my way please, I'd hate for the others to go the same way as they are growing quite big.

Hi Avant and welcome to forum.

First thing here is there is no such thing like bonsai seeds and there will never be. They sell normal seeds branding them as "bonsai" just to get uneducated buyers. Having that mind, such bonsai starter kits are pretty much non sense since its still only a seed, a pot and even sometimes without and description or basic guides or any learning material. And its not your fault, actually its nice you have interest in Bonsai, I hope you keep it. Bonsai art is something you learn and practice for many years before you get the whole point and it just requires parience and dedication. The starter kit will not learn you do Bonsai, but will defenitely teach you patience, that is key. Sorry, I cant tell what plants they sold you, but you have many years ahead to figure it while they slowly grow up. During this time best will be learn and discover all about Bonsai. Good luck.

Avant
We all start somewhere and I am glad to see you are interested in bonsai. With the seedlings you have it is impossible to know what you have until it is a little older. Maybe by summer we could ID it for you. Until then keep it out of direct afternoon and evening sun, and water when the top looks a little dry. With seedlings never let the soil dry out completely and don't keep it soaking wet either. I have a Japanese Maple seedling growing and I watered it about an hour ago. It might look discolored but it is actually healthy.

first pic. looks like a weed to me.
2/3 could be Ulmus Parvifolia.