Hey!
You got yourself some leaf miners.
These little bugs are larva that are eating your leaves from the inside out, when they get big enough they break through and leave..
That normally results in your little baby cannabis plant getting very damaged.
Luckly they can be easily found with the traces they leave behind.
So what can you do about?
1. Cut off all of the infected leaves. Which I read you’ve already done but they can occasionally come back. So now prevent. I see you’ve also done that.
2. Use a cannabis friendly pesticide, Spinosad work good and are organic if not something similar. I’ve used a similar version from Spain. It’s done the work for my outdoor crops in the past.
That should do the trick.
I’ve never had to use neem oil but I’ve read it works great.
I would re apply to prevent after about 7-9 days. And then check again, maybe even re apply.. be careful if in flower. People do use it but not spray, manually applied. Wouldn’t want any of that stayed on your buds.
Hope this helped.
Good luck and happy growing.