Hi its been a while since my last grow so needing a bit of help My plant is now about 4 weeks into its flowering stage its nirvana northern lights she was vegged under blue fluros for 6 weeks nice and healthy bushy plant during that time... I have put her under a 600 watt sodium light in my loft now for the last 4 weeks after the 1st 2 weeks the fan leaves have starting turning yellow and most of the larger ones have falling off Anyway I was just wondering if I should add extra nitrogen to her feed to help this or would this just complicate it more???? I am feeding her canna bloom which I was told is one of the best for budding stage and it does contain a little nitrogen but like I said not sure what to do thanks guys
It's a common and also somewhat tricky problem. As you surmised, your plant is running out of N too quickly. Could be genetic, could be your feeding regimen in veg, could be a pH issue. On one hand you don't want to add a lot of N in flowering because it retards bud production. And yet, you don't want your plant to die or suffer badly through flowering either. You need to walk a fine line to balance those two issues. First thing I suggest is checking your pH to make sure you aren't locking out N. If your pH is fine then I would suggest mixing half veg fert and half flower fert for your next watering, to boost the N a little. You could also use diluted urine, a good source of N but not much else. You will continue to see yellowing of leaves through the rest of your grow, just keep growing on. You may want to time your final flush and end of feeding at 1 week before harvest rather than 2 weeks before since your plant will have already used up much of its stored nutes already.
i would not worry too much about it. a N deficiency is physiological during the stages of flowering. of course in your case it might be happening a bit too quicly (got any pics?), but on the other hand the last thing you wanna do now is administer more N as this would compromise flowering. The sudden switch from fluoro to a 600W might also concur in the yellowing of the leaves. these type of changes should be done gradually to let the plant adapt to a new and much more powerful light source. anyways, good luck with your plants, mate! im sure the end result wont let you down!