If your not using Cal Mag, then start. It helps more than pple think. Also your leaves are pretty dark green, with a bit of tip curl and that could be the start of nitrogen toxicity-dark green leaves that are droopy are nitro tox probs. If your not watering with plain water PH'd to 5.8-6.2 every now and then, then start doing so. Id run water with Cal mag in it one time and plain nutes the next and switch between them for a while and see if that helps.
Its hard to judge based on a pic alone when we dont know your nutes, or have much of a diary to look back at and gleam info from. But aside from the leaves "not seeming that strong" as you put it, if there is no other issues that that, your doing well. Plant looks pretty good to me as well.
If you want to make your leafs and plant in general stronger you need to start applying silca like Rhino skin or something sim coming into wk 5. It'll help. Happy growing.
Different phenoms likely of same strain. Plus the ones getting less light tend to stretch more growing taller to reach more light. If you take them out at time rotate their positions in grow space is a healthy practice.
