Sad Seedling

Guess we are all different and it happens with the plants too. For them to die something bad must happen but if you keep taking good care she'll grow like the others. Also worth to note that at this phase, as you refered, the plant needs high RH. On the other hand for the roots to grow faster it's convenient that the soil doesn't stay humid too long. It's always a matter of keeping the balance. I like to use bigger pots at start and I'll increase gradually the space between the plant and water mark in the surface of the soil. Good luck