I think it's because your plants have used up all the nitrogen in the soil and as the plant is now starting to grow more top growth it's sucking all the nitrogen and other nutrients from the soil upwards and through the bottom leaves !! This in turn is leaving the bottom leaves starved of the nutrients they need to stay healthy !!! I've got a little plant now that the same thing has happened to its about 12inch tall but the bottom 7 inch of main stem is now bald where all the lower leaves fell off ...lol... My plant is now budding nicely though and stinks its also covered in chrystals !!! Take look at my thread grown with normal household bulbs in a pc case ...lol...(1 BAGSEED EXPERIMENT ) ... Oh yeah as I was saying ...excuse me bit stoned and rambling on ...ha ha..:rastasmoke: !! The nutrients in my soil where used up very quick because (small container)the leaves looked exactly like yours before they dropped off !! ARE U USING NUTES ?.. If not ask someone on here to help u with what to use .. The other cause of your problem which I think is the next biggest issue could be from lack of proper light at those lower levels (my plant also had bad lighting at lower levels) .....I'm no expert but I think it's either of those 2 probs and if your not using any nutrients now and your in rubbish soil then go with the nutrient option....but please ask one more guys on here first !!! :rastasmoke: keep us updated and check out my plant here Buddingplant's Library | Photobucket