massive stretch , can it be genetic

You are in the first week of flower they will stretch you want this in flower to build up your buds more stretch more buds its a good thing add more 660 and watch them shoot threw the roof:+1::+1::beers::beers:

As Michka said lights to far away. Your tent looks very crowded enough fresh air exchange is important. Consider more smaller lights rather than 1 big. A mix of light types has proven good results e.g. HPS & LED together.:v::skin-tone-2:

Hi ! Your lamp is too far from them.. Lower is better... 40 to 50cm above your plants will be perfect ! Your plants are searching for more light, that's why she stretch too much ! Wish you the best ! Michka