Why my seedlings first leaf buds look so odd?

That might just be a genetic mutation, and with regard to the slow start, all genetics vary a bit for growth vigor (and the age of the seed and storage conditions can impact this as well). Two things I might check to be safe: (1) watering habits - I water thoroughly (to the point of a bit of run off, then let the media dry so the top layer is dry (I stick my finger in the soil a bit to feel how dry it is and if dry I water again) as cannabis tends to like a wet/dry cycle. (2) Light - I use the free photone app to measure light intensity (with a piece of printer paper over my camera to work as a diffuser as instructed in the app). I use their recommended guidelines for reference when I grow. Here's the photoperiod page: https://growlightmeter.com/lighting-requirements-of-cannabis-over-the-full-grow-cycle/ And here's the auto page: https://growlightmeter.com/autoflowering-cannabis-lighting/ (You can adjust light intensity either by dialing the grow light up or down or changing the distance of the light to the plant (I hang my light on a rope (actually using picture wire for one light) and adjust height up and down.) But unless you are in a rush, I would give it another week or two and see what happens. Just my opinion, obviously. But you're posted grow diary looks great, so I think you'll figure it out. Hope this helps and happy growing!