Top leaf edges and tips turning yellow?

hello, please help me diagnose my patient:

strain: Nebula
substrate: plagron growmix
lights: 600w ndl
watering: every 24h
nutes: 4ml plagron algo bloom per 1l

the plants are in week 3-4 of flowering

as you can se the top leaf edges are turning yellow - any idea what this is?

[image]http://s1.directupload.net/images/131005/temp/3yza9dvc.jpg[/image]
[image]http://s7.directupload.net/images/131005/temp/5va67qsq.jpg[/image]


1. Are you growing from seed or clones? Clones
2. How old are your plants? 3-4 week of flower
3. How tall are your plants? About 40cm
4. What size containers are they planted in? 6.5l
5. What is your soil mix?plagron growmix
6. How often do you water and what type of water do you use and how much you give per watering? Every 24h tap water with nutes mixed in 1.5l per 5 plants roughly 200ml per plant
7. What is the pH of your water? No idea about 7 after testing with phtester drops
Also i just tested the ph of runoff water and its between 6.5 and 7 according too ph test drops 8. What kind of fertilizer do you use and what is its NPK ratio? Plagron alga bloom
9. Do you foliar feed or spray your plants with anything? No
10. What kind of lights do you use and how many watts combined? (HPS, MH, fluorescent, halogen, incandescent "plant lights") 600w ndl
11. How close are your lights to the plants? About 50cm
12. What size is your grow space in square feet? 1 sqm
13. What is the temperature and humidity in your grow space? 21c night 27-30c light14. What is the pH of the soil? No idea
15. Have you noticed any insect activity in your grow space? No
16. How much experience do you have growing? A little

Water pH too high and possible nute burn?

I agree with Thrice. Your pH may be just a touch high (your "soil" acts more like a soilless mix) and it also resembles early stages of nute burn. The HPS and the early stage makes it a bit difficult to observe. Good looking plant btw

-Sap

Ogracious said:

I agree with Thrice. Your pH may be just a touch high (your "soil" acts more like a soilless mix) and it also resembles early stages of nute burn. The HPS and the early stage makes it a bit difficult to observe. Good looking plant btw

-Sap

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and is that a serious issue? will i loose much yield?

any way I can adjust my soil pH using ph- ?

also over at another board someone is saying it could be too little watering - i water every 24h with a 1.5 liter bottle divied up on 5 plants so each pklant gets a 1/5 of 1500ml per watering.
the plants arei n 6.5l pots and the guy suggest to let em dry out and then water with 3-4liters of liquid each but less frequently?

eos666 said:

and is that a serious issue? will i loose much yield?

any way I can adjust my soil pH using ph- ?

Click to expand...

It is not that serious of an issue. Adjusting the pH of your water (AFTER you have added any nutrients you will be using) with pH Down before watering will help lower your soil[less] pH. Keep in mind, it takes about a week for it to equilibrate so don't expect immediate results, though it can happen much quicker depending on pH buffers in the medium. A bit of peat mixed in with the soil before planting can help keep the pH down as well. As for the nute burn, I would dilute your nutes just a little bit, possibly water once without nutes first. Hard to see the extent of it with the HPS on. Also, your nutes do not contain calcium or magnesium and I have no idea what is in your tap water, I would recommend adding some CalMag or a 1/4 tsp of epsom salt per gallon to your water. Calcium also acts as a pH buffer and will help stabilize pH. Good luck!


-Sap

I also would not worry about how much water, as it does not appear to be over/underwatered.

-Sap

here are sme better puictures:

Looks like nute burn to me. I would [over]water once with plain water then continue with 3/4 strength nutes and see how she does.

-Sap

It's Normal For Marijuana Leaves To Start Turning Yellow As Harvest Time Approaches, Don't Keep Adding More Nitrogen!

oh yeah and that is a potassium deficiency :
Potassium isn't absorbed properly when there is too much calcium or nitrogen in the system. Check the pH of your water, and flush your whole system with water that contains half the normal amount of nutrients and see if your plant starts showing signs of improvement.

chairroller said:

It's Normal For Marijuana Leaves To Start Turning Yellow As Harvest Time Approaches, Don't Keep Adding More Nitrogen!

oh yeah and that is a potassium deficiency :
Potassium isn't absorbed properly when there is too much calcium or nitrogen in the system. Check the pH of your water, and flush your whole system with water that contains half the normal amount of nutrients and see if your plant starts showing signs of improvement.

Click to expand...

I don't mean to argue, but it is definitely not a potassium deficiency. The fact that the veins are yellowing at the same rate is the determining factor. With potassium def. the meat yellows, followed by the veins.

Edit: Also, K deficiency affects old growth, not new growth. It DOES look very similar in that picture though, I can see the confusion. It also would affect flowering in a huge way, which it doesn't seem to have done.

Aha! Found the old poster...

so yesterday i flushed them with water and now ill try to recove them using water/rhizotonic and maybe some light nutes

Are you a Superthrive user? I would add a drop of it.

-Sap

plagron grow mix is soil not soil less - get your ph down to 6.5

You have nuteburn though - how big are your plants? Plagron grow mix has enough nutes in the soil to feed for 3 weeks - depending on how fast yours grew in 3 weeks will determine how many nutes are left in from the plagron

Your nute burn is not severe however so just feed with plain water phed at 6.5 with rhizotonic untill she stopps burning - then start up from quarter strength again