THCC Rider

First time grower and I've been working out how this all works as I go! I'm larning fast but my conditions are obviously not ideal so not expecting huge harvest, but it's only for personal use so if I get anything I'll be happy. Started with auto dwarf in soil, B&Q multi purpose compost in small pots. Flushed thouroughly first. Four regular seeds. Makeshift growing frame with baking foil walls, top and base. Lighting is an overly expensive Philips Hue Lightstrip Plus (standard 2m length, LED), which has an app for timing and colour temperature control, spec online says the lightstrip is 120 watt equivalent. Currently lights running 24 hours as I read autos are good with that, but most guides I've seen since say 20/4 so I'll probably adjust that if I get confirmation. All germinated within 2 - 4 days. Two germinated about a day and a half before the other two. One of the first things I read said that males tend to germinate first so I marked them 'possibly male' and the second two 'possibly female', but I haven't seen that since (moreover, that it can take weeks to tell sex) so probably a red herring. Three of them have grown the cotyledons and first pair of proper leaves and are about 4 - 5cm, colour seems okay (very slightly pale but nothing that worries me). BUT the first of the four to germinate got to about 2 cm tall, with a sort of bottleneck or pinched stem just below where the cotyledons and first pair started to appear. Now it's 8 days and the leaves are still tiny (and darker green than the others) and the stem below the bottleneck swelled up to about 2 mm thick (twice what the others are) and today the stem has a vertical split almost the whole length - it seems to have burst. I am guessing this is just a defect in the seed that was waiting to happen, and maybe the split only could have been avoided if I had geven it less water, but I think it's a dud. I'll let it grow though for now just out of curiosity to see if it repairs itself in some way at such an early stage. I've searched online but can't see anyone else reporting this so if anyone can shed any more light I'd be interested to know.