Part of the problem is the plant is in a huge pot for its size. That will slow it down due to potential watering issues and the fact the roots are working overtime to colonize such a large volume, it's probably focusing more on roots at the moment.
Big pot watering -- water a diameter just wider than the canopy, but make sure that moisture goes all the way to the bottom. Continue to wait for top 3cm to dry before repeating. Slowly increase diameter as the plant grows. In future it is far more ideal to use appropriately sized pots relative to plant size -- even for autoflowers. Potting up does not shock a plant no matter what people claim.. as long as you don't use some sort of kung-fu grip on the rootball... treat it carefully and you'll never have a problem. With ~400 transplants, i've yet to see 1 get shocked. Simply should not happen. proof is in the pudding and not just my experiences. Potting up is just gently placing the plant in a larger volume of substrate and does not damage roots or the plant if careful.
It's not too far back from vigorous growth if that is 2 weeks and looked fairly normal by 1 week, if that was 7 days from sprout in week 1. Probably should have 1-2 more growth nodes at least by 2 weeks. Some plants just don't grow as fast as others, too, so don't beat yourself up too much.
Reduce light a bit.. especially if you amped up even more recently. The nodes should have some distance between them by this point... Seems to be a bit too tight in the pictures comparing week 1 to week 2. Get some internode development going to ensure it is not stunted by light... Resulting internode length is your guide to fine-tune your light intensity -- too stretching - needs more. Too tight - needs less. Initially they can't take the full power of light but quickly demand it... take notes on timing of ramp up for future use... well this time you may not glean such info but next time when it isn't stunted take notes...