Light green top leaves with burnt tips on White Widow Auto

have you increased light at all lately? may take weeks to show such thing, so even if it was a while back. A less optimal environment may have caused the light given to exceed what the plant can handle too... consider any climate changes last couple weeks. otherwise, starting at the top helps eliminate possiblities if it is related to nutrition... it'll be a less mobile nutrient, if any. there are some toxicities that cause chlorosis in top growth -- too much P or K could do that, but you'd usually see coinciding problems from it also. Too much P would also cause some leaf tip and margin burns. These are at least somewhat mobile nutes, but the toxicity symtpoms are at the top. Can rule out low S, as the chlrosis isn't progressing petiole-and-out. A couple trace elements could cause chlorosis up top, but those would be rare and may not tie in with the burns. I'd wager slightly too much light, but could be wrong. If progression was slow, would require a very minor adjustment.. .few percent less power or a 1/2" more height etc... good start and see what happens with rate of progression. gotta do it.. Dingo ate my baby!