Yellow top leaves, sukphur defiicency? please help ;/

hi there my plants are in 38 day of veg , the strain is pure power plant, all are about 36 cm tall already. I started to feed them in 3rd week of their growth and they seemed to like it- fast growth, healthy leaves i feed and water them once a week , sometimes its 5-7 days intervals in between watering .the pots are 40 liters so i dont know how much water schould i use , i observe my plants mainly , how they behave and then i adjust water schedule . the problem has begun 2 weeks ago.yellowish tips of fan leafs ...on the very end like this:


and then after a week i found bottom fan leafs like that, brown , dry and dead middle part :



appart from that there is s sign of yellowing in the top and young part of the leafs which are new part of growth apeared after topping the plant ...the color is really different then other plants.this plant stays directly under the 400 watt hps so i thought its maybe heat but i checked using the hand method and it seems to be perfectly fine :



I watered them yesterday as i found them in the morning really light green and curly .last watering was 7 days ago, so maybe water deficency? i found this dead dry tips on every bottom fan leafs -all plants . all plants have this yellow tips as well ...and it seems to progress.
i feed them with biobizz- biogrow+bioheaven+bioroots every week -2ml/1l per plant.its organic liquid food .hope its not a sign of plant being burnt.My temperature was sometimes up to 31 C without co2 .humidity 40-55% , 2 fans-in and out air .1 lamp 400watt hps-on 4 plants .I dont know my ph yet cos i just got my meter.what do you think? could it be a lack of water?

the 2nd pic looks like the light is too close, the leaves are starting to cup upward at the edge (usually either heat or light too close) they also like a fan blowing over them for a light breeze. (was unsure about how your fans are set up)
the discoloration looks more like early Zinc dificiency (it is hard to tell from light angle if you actually have any discoloration, new parts are a little lighter when they first appear anyways). and the tips look like mild nute burn but can be caused by heat also.
http://growweedeasy.com/marijuana-symptoms

hope this helps.

do you think the water schedule might be proper then? this plant is directly under the lamp , but the distance is 36-40 cm , ill try to change her place in the growbox and see waht happens.but dry and dead tips of leafs i found even with plants in further distance from the lamp

overwatering can cause a lack of O2, you will see chlorosis(yellowing) all over. but like the post before, upward cupping is a sign that it cant transpire water ( salt lockup) so you may need to back off on your feeding. if your canopy temp is 80+ it will most likely be heat related. temp regulates all the other processes so i would put in a cheapo temp gauge with a remote sensor to get a better idea of the temp at the canopy........

is that one plant in a pot, or multiple? i couldnt tell by the pic

water schedule depends entirely on the plants, you could water more often without feeding every time. i usually feed once every week or so but water every 2-3 days, but again that is what my babes like. but 5-7 days seems like a long time between waterings

for a large pot once a week sounds pretty good, i like to wait till the top 1/3 of the pot is good and dry before i water.

yes its that one plant and just pictures of it. how on such a small amount of organic food i could get a burnt? we see how it reacts after water, but probably next week i wont give them nuts as all plants have a yellow tips.i check by my finger if they have a proper moist in a soil every 2nd day so thought its fine for them.but very often i used to found them with a temp over 30 C cos the fans havent worked properly in a growbox i have to say that all plants-fan bottom leafs have damaged ends-dry and crispy, but leafs in general looks healthy-except ends.Just this one plant got top of the leafs getting light green , the rest of them seem to have good growth ...i was thinking it might be due to the heat maybe and lack of water at the same time, cos she gets more heat and light then others and the same amount of water .so maybe i schould water more often and avoid the nuts for a while ?

the nute burn, if you do have any, also depends on what is already in the soil. i would say heat is the main issue.
what doesn't kill them makes you stronger, lol, thats why i like growing - 10yrs off and on and I still learn every grow.
good luck and hope your babes get better.

i gave them water, and so an imrovement today so schould be fine but im watching them very carefully

Hey, and here is the next chapter of my plant problems, 2 of them are beauties , another 2 struggling with kind of deficency , ive stopped giving them any nutriens cos was afraid of nut burn , but now i think it was due to ph levels that were far too high , over 7 so probably nutriens lock up ;/ could you advise what it could be by looking at pict of my plants? they have really big pots so maybe schould use more water and nutriens levels as well?

u no sometimes with all the will in the world and tips from here there and everywhere we most times when growing the herb should not over wory about plant problems ! although we will and they do need addresing but getting to the bottom of all our problems aint easy so my tip is never stress it coz were growin this shit to relieve stress so if u do the maths its say 3 months plus of wory for say one months or so worth of weed ( small grows of course ) that wouldent make sense, so my philosophy is chill as much as poss !!! good look with ur problems, lol ! peace out !

you're very right but what schould i let them die then? sometimes knowledge is the essential thing

please, could anyone help to diagnose deficiency?

shakti said:

you're very right but what schould i let them die then? sometimes knowledge is the essential thing

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of course it is and if u read between the lines u wud no leaving them to die aint the answer dumbo, lol, just chill is all wiv all ur problems and yes do ur homework also as ur doin but dont over stress it dooooooooood

i got your point man just tryin to find an answer , my plant has serious problems, today i used more water as the pots are 35 liters and gave them more nuts , we see what happens, would be really a big loss for me if they wont recover ;(