A little help here??

I'm on my 4th grow in a well ventilated 3X5 closet. I am using a 400w HPS for light and using General Hydro for nutes. My problem is everything goes good through veg and after I start into 12/12 my fan leaves start to yellow. I am growing in soil and I am about 4 weeks into flowering. The flowers are looking green but the fans are all turning yellow. Everything looks healthy but yellow. I don't show any signs of over nuting just yellow leaves. Any suggestions?? In some of my books it says it could be a possible (P) Potassium defiency. Any truth to that?? Not sure if you can tell much from the pics. Thanks

That looks like N deficiency. I'm having similar probs but my leafs spot then brown and curl upward as mg deficiency. Lock Out! I am thinking I have a bad batch of either flora bloom, floramicro or cal mag. The 1-1-1 worked well then I changed to bloom amounts and they crashed hard til I changed brands. Good Luck

beensoup said:

That looks like N deficiency. I'm having similar probs but my leafs spot then brown and curl upward as mg deficiency. Lock Out! I am thinking I have a bad batch of either flora bloom, floramicro or cal mag. The 1-1-1 worked well then I changed to bloom amounts and they crashed hard til I changed brands. Good Luck

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Spotting is pH more than likely. Drying up can be caused from fan blowing to much on plant. Point fan up away from plants but to still allow for good air flow around plants.

Sounds also like when you move to budding cycle you are losing nutes. Some strains eat up on the nutes when switched over. I start mine at 7800ppm then each week I go up from there. Nutes get stronger each week until just before harvest when I do my flushing for 5 days.