Hey buddy welcome to AFN.. silly question time but is it actual yellowing or just light green?? In the pics they all look a little light green which to my totally untrained eye just looks like fresh new growth?? They look great size wise for 12 days so could it just be that they're putting out fresh 'light green' growth fast?? That said one does look noticably lighter. Subbed to see how you go brother. Good luck
https://www.autoflower.org/threads/...g-the-auto-limits.57281/page-103#post-1921146
Well worth a read but wise advice from Archie.. maybe best to just let your first few go their own way to get a feel for growing a plant :smoking: your shout of course.. good luck.