Pinapple Chunk

Hey @alanwaters, I don't think this is caused by nutrient issue - that would almost in all cases cause leaf tips being burned. My vote would go for minor light stress as it looks like edges of leaves are turning up. It is a young plant so she definitely doesn't need a full power of the lights you have - she would be more than fine with 200W LED. Try to check the documentation for the lights you have but I would go a much further than 40cm with the 600W. If you have dimer on the lights, lower the power to ~50%, or if this is not an option I would go as far as 60-80cm depending on factors like reflective material on the walls, overall temps, RH etc. With such a powerful light this close it is like putting a young plant to full sun...as the saying goes, less is sometimes more 😉 But your plant is still looking healthy so if there is any issue, it is just minor one and she should get better very soon. Good luck and happy growing!

Dude, if you are going to grow on coco, a pH meter and EC/PPM meter are a must; be sure to use them. As for your question, as long as your feed lightly, there will be no salt build up. If you want to go ahead anyway, then yes add nutes after the flush, since coco is an inert media and has no nutrients on its own.