One of the plants has only one leaf and does not g...

Its a mutation and it'll most likely grow out of that in a week or 2 but could have some funny looking leaves later on in its life. Hope this helps.

growdiaries.com/diaries/52015-royal-gorilla-royal-cookies-grow-journal-by-asnoriu/week/253457 Scroll through week, i called her bunny gorilla, you can chase her in this grow by name. No ossues at all.

Sometimes it happens, mainlining by nature. Had 2 such mutations, both ended well and big.

Genetic mutation..........by the looks of it, there appears to be 2 branches sprouting from the first node and these should take over. It is doubtful the main tip will grow further. Seeds are random organic products, not machine made items guaranteed to be flawless. BTW, clear cups are a no-no for seedlings, roots need absolute darkness to form properly. Anyway, transplant asap, they are about at the limit of those tiny cups anyhow.

Hello, its genetics off that plant. Nothing to worry, in past i have couple off similar girls who at the end give very pleasant smoke. At some time it will produce normal size leaves