Hi Growers What could it be?

By the looks of things, all the answers here are partially correct. Calmag lockout, possibly salt buildup in the soils, which will affect pH values. When this happens to me, I deleaf all affected leaves except the sweetleaf of course, do a double flush and add fresh nutes at a reduced strength. Minor setback of growth but will reverse the trend.

Week 5 last picture : it is a ph fluctuation or an over feeding. Check the water runoff ph and Ec then correct to the good values. Maybe houdini can see another issue but I can't

hey there sorry to disagree with everyone on here, but it's clearly magnesium deficiency , you can tell from the burning starting at the tips of the serrated edges of the leafs and spreading inwards , keep feeding the cal mag, but you can also make a spray 1ml/L and spray at just before lights on or just before lights off... that or reduce your light schedule slightly which should solve the root cause of the problem. Hope this helps ! 🚀

To me it looks like alightburn. because all leaves n one hight are affected. In Week 5 the brown spots look like spilled nutrientsolution on the leaves, and the lights burnt the little drops

@RasChannel looks like your plant may have a nutrient lockout due to incorrect ph level in the medium. Try a flush with plain water then refeed at half strength ph'd at 6.4

Hello my friend I think you have fattened your plant too much🤐 You should just water once or twice in clear water PH 6.3👍 May the force be with you💪