I got this baby for cheap, knowing it would likely be hard to make it grow healthy and thrive. 2 days after i got it, one of the 2 leaves yellowed and i had to cut it off. it's currently in a potting mix of soil, perlite and sphagnum moss, and i've been trying to keep it moist. it's under my grow light.

im nervous cause i feel like the remaining leaf is kinda yellowing, and i don't wanna lose this baby 😭😭 help!! the first photo is how the leaf was when it arrived, the second is how it is now, slightly yellower.

oh, i'm in brazil and it's spring here right now.

is yellower today. i'm desperate 😩

Its too wet.
Cuprea is considered a Jewel Alocasia. They don't like to be kept wet. Remove the moss ASAP, and don't add any more water to the soil until its almost completely dry
It MAY go dormant. If it defoliates, keep in in the warm sunny place. Don't fertilize it hoping to spur new growth.
If it resprouts and starts growing again, don't overwater it.