Can you help ne again Why are the internodes short?

Autos can be interesting little buggers at times. I think your plants look perfect for the stage you're at. If you haven't noticed and preflowers showing up, you should soon. There's still plenty of time for these plants to grow bigger, most of your growth in autos happens in early flower. Up until now your plants have been focusing more on establishing a rootzone. I've seen plenty of autos this size finish 6-8' at work so don't fret yet.

Just means they're getting enough light and don't have to stretch towards it.

I'd start giving a low dose of grow nutrition. Some enzymes. They are at a good place. Autos can take from 3-6 weeks generally it's 4 or thereabouts. Yours will take a massive growth in the next week when they prep (stretch before pre flower) and they'll double maybe triple and you'll get big nodes. Been autos. And having a good base. Maybe try top one also. This will give huge nodes. It'll give you tons of experience also. Autos also like rest. So, try not overdo the light. 18hrs 4-500 ppf max.. Good luck. Looking nice & healthy. If you have rich soil nutrients. & organic bloom nutes you can add them when the stretch happens. As they will need extra NPK.

Your plants look healthy. Your node spacing looks fine. This is part light intensity and part genetics. If you want a lankier plant, reduce light intensity. Some plants are just shorter and bushier. Don't try to force a square peg through a round hole. i.e. don't reduce light too much. that'll only have a much greater negative effect on outcome than whatever you are trying to accomplish today. Short doesn't necessarily mean it'll be a low yielding plant. your leaves aren't tilting downward. The plant is holding up some nice healthy-sized leaves. you are finen there, too. Autoflowers don't typically grow to be large plants. Expect a 50-100g plant more times than not. What you would expect from a photoperiod with 1-2 weeks of vege phase and the same time frame, but more predictable / consistent. Don't allow anxiety or OCD to cause an unnecessary reaction.