Tangerine Dream auto

you'd likely see other symptoms if it was the light causing it... My money would be on a little nute burn. Since it took this long to show up, i'd be conservative in any adjustment. I don't see a diary, so a bit incomplete on information. Whether soil or soilless, for example, would impact suggestions. if soilless, calculate PPM from your guaranteed analysis labels. compare to any week of my journals with a set that works well at 6.0-6.5pH and intense lights. This becomes very easy to find a happy zone that works well for vast majority of plants. ensure 10% or greater runoff to avoid buildup. I'd guess p-tox based on symtpoms (below) but with this sort of information at your fingertips, you can be more certain with a little math and rule out many things, making the answer very apparent. if not hydro or hydro-like nutes, then it's more of a balancing act. Based on symptoms i'd guess P-toxicity. New growth is a bit yellow with slight contortion / thin blades and tips burnt on some leaves near top. if you start to see spots, i'd guess that is lockout from this tox, too. But, what you've been feeding so far and what was in your soil to start need to be considered and weighed. Again, it took a long time for this to show up, so adjust slowly unless it takes a distinct and precipitous dive.