I've read that very low humidity can also contribute to a k def and yours IS very low. Would bowls of water sitting around help at all? I still think you are looking at some sort of lockout however......

Good luck.
Weedhound Reviewed by Weedhound on . Brown spots, potential MG deficiency.... Your thoughts are requested!! Interesting situation, New York City Diesel in three gallon container used for propogation purposes. Cuttings were taken from this mother plant one week ago at which time she started to develop these odd brown marks on her fan leaves. The brown marks only appear on the established fan leaves and not on new growth. The clones taken from this mother have shown no signs of browning. Each of these fan leaves also curls. Current room statistics are 85 F, 26% H (it's winter no way to raise it, Rating: 5