First leaves on one of my plants getting yellowing.

Low on N relative to growth rate. pH would lock out Ca long before N, so that's easy enough to rule out. If it was nute lockout you'd probably see something building up (tox symptom of some sort) which is absent, too. Up portion of N in your fertilizer mix in small increments, waiting between to see how each step impacts the paling. Things won't necessarily change overnight. Paling can heal, but if it progresses beyond that the damage is permenant.

Your over watering your plant. When it's that small make sure your giving small amounts of water. Make sure you let the soil completely dry out like really dry out before watering again. Also dial back the light a little bit. I'f it's an option put the light at 50% of what you have it at rn for the 1st half the day then put it on what u have now do that fir a few days. That helps it recover some from the stress the leaves are starting to twist that's usually the temp and humidity is off and over water and to much light. Hope it turns around for

For me, for now they have nothing, if you see that the others are also turning yellow, start trying to understand if you could have done something wrong during the repotting. Are you using a rooting agent?