How can I fix this plant?

Did you spray them with anything with the lights on? Looks like what happens when you do- as Roberts said, they look a little warm?

You're worried about the cotyledon which has finished it's work and will die off anyway.. The mottling of the true leaves is most likely just the wonkiness of early leaves - they, too, will die off and are of no concern right now. I could also be simply the genetics and you've got a mutant - but there's nothing you can do about that and nothing that you have done wrong to cause this... Relax!!

Looks like it might be getting too warm

There is nothing you can do to "fix" this, just be patient and give the plant a chance to get itself established. Quite often the first 1-3 sets of leaves can be a bit "funny", but the plant usually sorts itself out all by itself, generally once it develops a decent root system. It is too young to be suffering from any deficiencies, as long as you started with any sort of half decent soil that is. However, not all seeds are perfect, some just don't make it........but give this one another few days and most likely it will be fine.....if not, you will know then, that this seed was one of those that just don't make it. It always pays to plant more seeds than you need, for those times when you get a dud seedling.

Someone??? Pls 😁