Excessive streching, or is it normal?

high heat and humidity can cause some stretch. Congestion can cause stretching too, because low-light hitting leaves (all of the shielding of tightly spaced stalks) will make it reach for more light. Genetics is a primary factor, of course. Everything will be relative to the genetics. go for 2-3 colas per sq ft.

4 plants + one bucket = massive competition = excessive stretching. In future, 1 bucket, 1 plant.

its strain specific

some strains have sativa dominance so they will stretch quite a lot in future you can use training techniques like lst or hst to keep the canopy even and avoid the legginess