After the stretch is over (2-4 wks most strains) less N is needed (hence grow/bloom N ratios).Very dark green leaves is N toxicity.slightly higher of 6 PH in flower is ok.
Be carefull when chasing deficiencies in a plant when it is in late flower for that particular strain.It could be grower error or the plant doin what it does.Keep up a healthy enviroment,and a reduction in nute strength in days leading up to known harvest is good.
A Hempy plant will benefit from a res reset to be safe than sorry.
Take room temp PH 6 water (6 PH being important),and flood the zones above drain hole (plug drain hole with finger if needed).Smell the run off.If the run off has any foul smell,and you are running a sterile res?Then you have root rot.If no smell then repeat a upper zone flood with with nuted water (less strength if over nuted is suspected).The plant will benefit from more than one upper zone flooding with PH'ed water if build up of precipitates is the problem.
Simple/cheap root rot cure for a sterile Hempy res.Reset res with a mixed equal volume of PH'ed water,and 3% over the counter Hydrogen Peroxide.Plug drain hole,and let solution flood as much of above drain hole as possible for a minute then let drain.If needed repeat.This also helps with nute robbing light leak Algae growth.
I also use 1-2 drops (pipette drops not cap drops) of regular bleach per gal of nute solution for regular maintenence.Let 30 minutes go by before using a bleach treated nute solution,and note that going more than 2 drops per gal of bleach is more risk in harming plant.
Please note that for general maintenance I will put a couple capfulls of 3% to my hand feed cup,I mostly rely on bleach.The 50/50 water/3% provides an instant aerobic enviroment to fight backpathogens. A thourough flush once in awhile will be a preventive measure to avoid this unless medium is heated,and stagnat.
Using organics,and bennies can be done in Hempy,but do a search,and see for yourself.Sterile res,and readily available to the plant hydro nutes for me.
I hear people say bad chems in over the counter 3%
hydrogen peroxide H2O2.I am still searching for bad chems.From what I can understand the low dilution needs stabilisers to keep the extra Oxygen atom in solution.The stabilisers are PH buffers that maintain near nuetral PH.These buffers are chems that we use to make foods,and pharmaceutical products.Sulfuric acid
is a DIY PH down,a plant nutrient (just do not apply undiluted),and a popular stabiliser.The others help certain styles of dough rise,and stuff like that from what I can find.Some health nuts drink it.They drink a dilution of food grade 35% because the stabilisers in 3% will upset your stomach.When in doubt,get the 35%,and Google popular dosages for Hydro.