who is they? I have had clones that were nothing more than black sticks with one dried up leaf on it make it. Glad to hear it worked out!
looks like too rich of soil burned the small thing to death or if there is small white or black dots on the bottom of the leaves it might be spider mites. either way maybe try switching your soil mixture for a early veg recipe and invest in a ph meter
I did switch soil and the plant is doing great...both pics are the same plant. no mites we look evey day..runoff ph 6.27 soil Promix bx...started with mg ..but i didnt know any better giving it a mild 20 20 20 about every 3 days water as needed