Yellowing leaves. 5 weeks into flowering. Advice..?

[enindable]

Hi there, got a problem with my Powerplants. Yellowing started about 1 1/2 weeks ago. Feeding the girls Natures Own Super Bloom 1.9.1 with a light drop of Meta K, under a Lucragrow son-t 400w on 12/12, 5th week into flowering. An average temp around 25d (74f). PH is 7-8, quiet high... could it possibly be nitrogen deficiency, ph out or K toxicity? any ideas would help. cheers.

[FreeDaHerb]

Hard to tell with the HPs light but looks like a Iron or Zinc deficiency to me which happens at high PH's as it's mostly unavailable to the plant in that range, most likely your high PH is the problem..and of course plants normally do yellow and lose their leaves as they flower but yours are doing it a bit early which might affect yield somewhat. Can you get us some close up leaf pics under regular light with the HPS off? Is it the older parts of the plant or the new growth?

This might help..from onlinepot help area

Nutrients PH Problems On Marijuana Plants Spots Symptoms That Appear (http://www.onlinepot.org/grow/PHfluctuationsornutrients3.htm)

Zinc Deficiencies


Deficiencies appear as chlorosis in the inter-veinal areas of new leaves producing a banding appearance as seen in figure 18. This may be accompany reduction of leaf size and a shortening between internodes. Leaf margins are often distorted or wrinkled. Branch terminals of fruit will die back in severe cases.
Also gets locked out due to high pH. Zn, Fe, and Mn deficiencies often occur together, and are usually from a high pH. Don't overdo the micro-nutrients- lower the pH if that's the problem so the nutrients become available. Foliar feed if the plant looks real bad. Use chelated zinc. Zinc deficiency produces "little leaf" in many species, especially woody ones; the younger leaves are distinctly smaller than normal. Zinc defeciency may also produce "rosetting"; the stem fails to elongate behind the growing tip, so that the terminal leaves become tightly bunched.

[dejayou30]

Its hard to tell how yellow they really are with the HPS lighting, but remember that some plants may start to yellow towards the end of their life cycle, as they are consuming their last remaining energy to put toward bud production. At 5 weeks they are on the downslide of their flowering life cycle and may be using stored nutrients before you harvest. But with your high pH nutrients could be getting locked out. I don't grow in soil so I am not of much more help. Good luck! :thumbsup:

[enindable]

Here are some closer photos. It's been getter worse over the last few days, browning and curling on the tips. this problem is only happening on a few plants yet they've all been getting the same feed.

[FreeDaHerb]

Water them with a high P/K nutrient solution with a low PH of like 5.5 - 6 and you should see some improvement..your PH is the answer, obviously.

If you have access to General Hydroponics 3 part Flora series use the Lucas Formula of 8 ml micro and 16 ml bloom per gallon of water, maybe start at 50% strength in thats same 1 - 2 ratio and see how they respond. The PH should be just about right for your situation without any adjustment if you start with clean RO water. I would water them until it runs out of the bottom of the pots and catch some of that runoff and test it if possible..ideally you want it coming out lower than 7 or yellowish green color using the test vial with indicator drops.