That is a lot of cobs in a 4x4 bro.. what kind of wattage you running across them? By the look of your leaves they are loving it, im assuming 300-400w. I have 16 across a 4x8ish section in my 8x8 tent and only run them to about 600 to 650w in flower depending on strain with great results for years now.. i have the ability to run them a little over a 1000w, but cant get close to that with the panels raised all the way to the roof.. just too intense..
I added some uv and ir to my panels last week.. time will tell if its worth it.
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Cheers