Possible Phosphorus deficiency?

[Auto gorilla 575]

Evening all had a look in on the lady’s this afternoon and found a couple of leaves looking abit curled up and what looks like darker brown patches appearing it’s only on two of the three cuts I’ve got and not showing at all on the one plant grown from seed. 
They are all in the same Rdwc system

EC is sitting at 0.8 

I don’t PH my res as I’m using advance nutrients ph perfect sensi grow line of nutrients the only other thing I add in is silver bullet roots. 

res temp is 19c 

lights on is around 24/25c

lights off is around 20c

light schedule is 18/6

humidity has been in the low side and sits around 40/50 I know this could be abit higher but not sure it would cause this to happen. 
anyway anyone have a clue of what could be up with them help would be much appreciated. Cheers. 

[Guest]

It would be much more helpful to have a picture of the plant with the leaves on. If that last picture was at the top of the plant I'd say heat stress and environment. That's a guess though really without a plant pic

[greenvigilante 1,836]

as said full pant pic needed but also what is the background ec of your water?

 

i mean if u are using ro you are still only giving them 2ml per litre

[Auto gorilla 575]

@FatBoy77ill have to get you a full picture of them tomorrow when I’m back with them, these leaves are not from the top of the cuts more around the middle section and lower down. Defiantly can’t be heat stress as my temps have never been over 25c my environment is dialled in quite well. 
ill get some full plant shots up tomorrow see what you make is them. 

[Auto gorilla 575]

@greenvigilante the back ground EC of my water is 0 as I’m using RO water. 
Water round here is terrible straight out the tap sits at 0.8/9. 
I didn’t really want to Take the EC any higher than that as these zcube cuts seem to be quite light feeders so far. 

[Owderb 28,538]

@Auto gorilla

 

Are you adding 20% tap water to your RO because thats the way to do it

 

Owd

[Auto gorilla 575]

@Owderb 

No I’ve not been adding any tap water to the mix.
 I contacted advance nutrients they said there is no need to as this line is aimed at RO water.

 I was curious about adding calmag but they said there is no need to.
 My last run in dwc I used pure RO water the whole run and didn’t have any issues like this that’s why it’s got me confused.
I’ll get some full shot pictures up later, the leaves do look quite dark might not like the EC being at 0.8. 

[greenvigilante 1,836]

@Auto gorilla  yeah bro dont add calmag as this stuff is made for the RO water yanks have to use cos there water is garbage

 

with u using ro 0.8 ec will be fine ws just incase u had a background of like 0.2 or something and they woulda been fed light

 

fire up some full plant pics tho 

[Auto gorilla 575]

I defiantly won’t be adding any calmag. 
ive always thought of using RO water it defeats the object abit if you add tap water back to it maybe in wrong though. 
anyways here’s a photo of each girl lights just came on so excuse them if they look a little droopy. 
number one 

she looks all healthy to me no signs of anything going on 

number two 

showing whatever it is on a couple of fan leafs one lower down on the right and one mid left still growing quickly though. 
number three 

she’s the worst and is showing it on multiple leaves as you can see the lower right and left mid/top right 

here’s a group shot 

the short cabbage looking indica Dom front right is not showing any trouble at all. 
Hope that helps 

what’s are people thoughts? 
cheers 

[Owderb 28,538]

36 minutes ago, Auto gorilla said:

ive always thought of using RO water it defeats the object abit if you add tap water back to it maybe in wrong though.

 

You need to put some of the minerals back in but in smaller amounts. Calcium being the most important. Thats why folk with really soft water suffer with Cal/Mg problems

 

Owd

[Auto gorilla 575]

@Owderb thanks so you would say this is a calmag deficiency then? Strange how only 2 of the four are showing symptoms though. 
when I change the res this weekend I will use 50 litres of RO and 20 litres tap water and see if that helps out then. But will this then effect the amount of nutrients I mix in? at the moment the EC of 0.8 is made up of purely plant specific nutrients. And then if I use tap water say starting EC of 0.2 they will only be getting 0.6 EC of nutrients from the bottle? Does that make sense!! 

[Owderb 28,538]

If you are using 50ltr of RO then 10ltr of tap will do the trick. 20% tap water

 

Owd

[Auto gorilla 575]

@OwderbMy res is ruffly 70 litres when full but is that what I should be aiming for 20% tap with the RO? 

[Owderb 28,538]

If its 70ltrs then 55 RO and 15ltrs tap

 

Owd

[Auto gorilla 575]

@Owderb thanks I’ll give it ago this weekend will also save some some time not having to make so much RO. 
Ill see they they respond they are still growing rapidly.