Banana Hammock hurting!

Need more information in your dairy like tent temps and medium temps and feeding EC/PPM. I don't see much indication of over/under watering in your updates, its good you switched them from 24/0 to 18/6 plants do need sleep. I would guess this is from heat stress and lack of air movement. If you are using the Sunblaster LED strips that are just white light, the plants can get crazy close with no ill effects. I did a OG Kush grow and they got right up to the bars "90w in total 5x18w 18" strip bars" and were fine. I also like how the plants grew under them. For my main set of lights I combined the Craft Cannabis Sun Blaster LEDs and their 6400k white ones. I did get some burn under 12" as Craft Cannabis LED line is much stronger but still a nice set of lights, the company does not have much information on any of them in terms of efficiency or par maps but they are a average for the whites and pretty nice for the Craft line. Still not super high end growing lights like some brands but they work well! Good Luck!