Had the same problem with my first indoor grows. Also a 600W light which kept them pretty compact. But looking at other diaries, not all hope is gone. I've seen many darlings that were +/- 15 cm after 4-5 weeks, but still managed to reach the 70-80 cm at harvest.
Next grow I'll (also! 😀) put them under a 150W 6500 kelvin light I bought recently.
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