What is the problem with the plant ?

WHAT!!!!. YOU DO NOT DEFOLIATE THE LOWER PART OF YOUR PLANT. As the bottom of your plant lacks getting light energy you NEVER take what little energy leafs that are taking in the light. As those leafs aren't supporting any growth, like nodes, it's just reached the end of its shelf life, it happens in every grow. The leafs before the node or nodes taken by doing mainlining will die off, it's just part of the process, your plant is prioritising where the energy needs to go. "Take the leafs below", lol. This happens it's just by passing the leafs to feed the node above. If you still had the nodes below that you took off and they were like that, dead leafs past sets of nodes then you worry. Is there any leafs like that above the any nodes? That's just getting my passed and used for food for the n9de above it. As when you take the node below all the energy and leafs in between will go like that as the nodes above you have increased their energy uptake. As for y9ur nutes I'll have a look now. I'll DM you about your nutes after I have a look at your diary. But as for the dying leafs, 100% the norm. If you have leafs like that after sets of nodes then there's an issue but just by looking at that it's clearly just the natural process. I'd leave them as they aren't even fully dead yet, meaning there still a point of food source. Or you can remove them as their energy is going anywhere hence y they die off. Good luck bro.