Have you got any photos today mate? I still think 60cm is too close MAYBE for the size of your plants. You've got 300w of cobs in there PLUS 250w or so of led. That's a hell of a lot of light.
I leave my cobs (only 200w) at maximum, height I can do in my tent. I have limited height as they are all sitting above tube heaters which takes about 25cm of height away. So seedlings start off at around 100cm from cobs and just grow up into them. They seem to like this and are getting some fairly good height on them.
My biggest plant is the Toofless Alien and her main cola is now only 40cm from the cobs. She struggled with this for a while and ideally I think it's not enough. I may be able to get another 5cm if I raise the light absolutely as high as it will go.
Basically, in my humble opinion, cobs are EXTREMELY intense. The younger the plant the further it wants to be away from the cobs IMO. So the way mine is set up seems to work ok.
Just trying to help mate as I'm not experienced, but I can tell you what I'm experiencing right now. Hope it all goes well dude.