Leaves are cunning why temp is low light is far

Oh no, math fail... and then "your" instead of "you're" ... Schools in the usa don't seem so bad all of a sudden by comparison, eh? Please don't look up my comments filled with typographical errors, lol.

LOL @FuzzySnout Your right! this is why I don't math when I'm tired.

Looks like it might be a hot spot from light being too close. Is there air circulation in that spot th plant is?

@m0use When I was in school, 4x4 was equal 16, not 8 ;-)

https://www.growersc.com/product/roi-e720 There does not seem to be any PPFD maps for this on their page or their manuals/spec sheets. It is a very powerful light if the stats are true. One quick google said to hang it quite high. lol Check you leaflets that came with it to see if it suggests any hang heights of any mention of its PPFD, I saw one mention that it provides 1870 PPF with a boost feature of 2080 PPF and that's a lot of light! Try limiting its power to 40% if you can or raising the light by 10" and seeing if it gets any better. 40% of 720w = 288W Your tent is a GT 48"x48"x80" by Vivosun or 4x4feet aka 8sq ft. 288w / 8sqf = 36w/sqft and that's more then enough. Anything between 28-35w per square foot is good. Obviously more efficient lights are stronger. at 50% its aorund 45w/sqft and that's a bit much. So its likely to much, If it does not go below 50% you can also chnage your lighitng schedule form 18/6 down to 16/8 to help give it more downtime. The golden metric for measuring light is something called DLI. google it and read up on it. calculating DLI is easy with PPFD maps. Email your manufacture for some they should have them. A DLI of 35-40 is ideal for indoor growing and this can happen from being on a lower % dim on 18/6 and then a higher percentage dim on 12/12. Eg. my DLI is 37 veg/flower @40% dim on 16/8 and @60% dim on 11/13 "on/off" In short its likely the lights.

As far as I can see it only happens to a taller plant, doesn't it? I think it's a light stress.