please help. possible nutrient problem, dont know for sure

i did some research and im thinking that i have a phosphorus deficiency problem. im using recommended amounts of nutrients. unfortunately i have fox farm, i heard that it sucks but i have not completed my first grow and i cant give an appropriate opinion on it yet. anyways here's some basic info.

just started 3rd week flower
3 biggest plants show same basic symptoms- red-ish stemmed leafs - mostly on older leafs, spotty dried out patches- only on 3 weeks or older leafs (kinda looks like fungus but only starts on leaf not stem), yellowing leafs and the pictures will tell the rest.

What is recommended? NPK value and how much Do you water/feed or ?

well when i say recommended amount i mean that i use proper measurements of solution in my waterings. specifically i use the foxfarm watering chart and i water probably once every 3 or 4 days. every time i water them i water thoroughly so all the soil is wet and water is coming out of the bottom. i wait until top soil is not wet and easy to comb with my fingers to water again. do you think im under watering?

Fa Fa Pho Twuny said:

well when i say recommended amount i mean that i use proper measurements of solution in my waterings. specifically i use the foxfarm watering chart and i water probably once every 3 or 4 days. every time i water them i water thoroughly so all the soil is wet and water is coming out of the bottom. i wait until top soil is not wet and easy to comb with my fingers to water again. do you think im under watering?

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Do you ever just give Ph'd water only?

lime73 said:

What is recommended? NPK value and how much Do you water/feed or ?

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Still no answer...
Probably need to flush! Lock out due to salt build up! showing as a dif.
Soil/Hydro?

what are your temps? when you feed do you use exactly what the bottle recommends, or a percentage? what kind of light and how close? I would recommend a flushing. and watching. whats your ph at?

temps flux between 68 at night and on a sunny day 85. i feed what the bottle recommends, no percentages. 1k hps and my ph is right around 6.
i just flushed like 2 or 3 waterings ago and the plants seemed to do a lot better when i did. i will give that another try, except i will flush a whole 5g bucket through this time. (there in 2g containers)

Fa Fa Pho Twuny said:

temps flux between 68 at night and on a sunny day 85. i feed what the bottle recommends, no percentages. 1k hps and my ph is right around 6.
i just flushed like 2 or 3 waterings ago and the plants seemed to do a lot better when i did. i will give that another try, except i will flush a whole 5g bucket through this time. (there in 2g containers)

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there may be two problems with what your doing, first its always a good idea to give your plant 1/4 to 1/2 of what the nutrient bottle recommends, as marijuana is a bit more sensitive than other plants, second,l depending on your plant size you may want them to be in 3 to 5 gallon containers, a good rule of thumb is 1 and a half gallons of soil for every foot of growth, or about 1 cubic foot of soil for every foot of growth.

i could be wrong about the 2 gal containers. i looked at them and compared them to a 5g bucket and they look like 3 gallon containers. i will try cutting the nutrient amounts down and see how that goes. thanks