your lights can only reach so far, your shitty looking leaves are no longer getting any light. So now they are redundant and your plants are rejecting them.
For your first time switch to flower now and cut off anything below the 5th node, you could cut of more but your first time this will be more comfortable for you.
You are doing great other wise so keep up the good work.
Also put a tomato cage over your plants . I bet you will need it and it is better to put them on before you start budding
Keep on keepin on bro