Firstly, this is a textbook, beautiful mainline you have going here👍. As far as previous answers are concerned, there may be some merit to the suggestion that you’re over feeding nutrients. Regardless of the soil mix you’re using however (and I have no experience with BioBizz’ mediums) I’d be surprised if there’s enough residual nutrient in the medium to keep the plant happy after the 5th week or so of veg. If you’re feeding with every watering however, that may not be the case and they indeed may be getting too much. If you’re already staggering nute feeds every other watering then I would be more inclined to suggest that this is a very small, localized problem that may actually clear itself up. The tips are only slightly yellow so this isn’t necessarily a sign of burn and the issue appears to only be presenting on one leaf. If you’re really worried about it then I would either stagger your feedings every 3rd watering or reduce the overall mix ratio by half. If it were me, I wouldn’t necessarily change anything just yet or worry too much about this at all. I’d just keep an eye on it for the next week or so to see if it advances at all and then re-assess. Could just be a wonky leaf and that’s a common occurrence. (Ain’t calmag either I would say as your already well supplemented there). Good luck!