Nodes

Been growing a few years now I've always been growing from seed anyway thought I'd try a few star dawg seeds well 5 out of 5 cracked and still growing well 3 and a half weeks old now about a foot high under a 400 hps light in coco pebble mix feeding canna a&b at 2ml per litre as I've always done with no bother anyway to the point I thought they looked a bit odd I realised they don't have any side nodes coming out of the main stem can anybody tell me what is going on I've never seen this before?

Check ya ph and check ya EC to start with . They got a canny stretch on them . Maybe ya have ya light too far away causing the stretch