NOOOOOOO THERE HUNGRY 600 ppm is way to low
Alot of my leaves did that and I cut alot of the fan ones off too, now i think theyre starving and dying bc of it. I guess ill just blast with light and feed em till they puke idk what to do!if they were that bad nute burnt for my time in growing they wouldent be there as they would drop off
play it safe raise ur ppm to 1100 then to 1200 flush then 1200 1300 hen they should be ready for final flush
don't mean to hijack the thread but I have same problem trying to figure it out am n flowering 4weeks I flush her today
4 weeks into flowering is still early. Have you tried using more Nitrogen in your feeding mix.
Im a noob but that looks like mag or potassium deficiency....you could just defoliate but id give it more p and k and spray like epsom salt mix on the leaves..