First grow

Its the genetics. Indica generally have fat leaves and stay short and squat. Sativa have thin leaves and stretch taller with more branching. Yours is an Indica leaning hybrid anyway, but it's possible it leans even more heavily that way than another seed grown alongside it - hybrids are often unpredictable. There's nothing wrong with the plant, don't worry. Lots of nodes tight together makes for large, dense buds. Plus it will stretch at 50-100% when it starts to flower. Just keep doing what you're doing! 😀

I would check your ph first. It looks like you are not giving enough potassium for flowering. Which if this is low your substrate ph will climb out of range causing lock out. The spots are calcium, and possible potassium deficiency spots mixed in.