Nutrients for stretching in week 1 flower.

Another thing I never see mentioned (though I've witnessed hundres of times). The pot/soil/root space profile (like narrow but deep or shallow and wide) also influences the stretching dramatically.

*err, I don't grow things indoor

Auxin, cytokinin, gibberilic acid, jasmonic acid, etc balance. Basically hormones. Many things can influence that though and I grow things indoor so I can't really say. High ambient lighting and heat, as well as low direct lighting can cause plants to stretch, for instance. Somewhat excessive nitrogen, potassium to some extent too.

with extra N, there may be potassium deficiency signs near the end of stretch. then you can focus on bloom nutes more.

extra nitrogen in this phase for max stretch. boost some more N in it and stretch will maximize. if you can find, get some amino acid based fertilizer for plants, amino works great during stretch

I mean stretch not stress.