Not sure what's up here ~ Brown/Rust spots on 2 leaves???

[AutoFiend]

Been growing a Greenhouse Seeds Big Bang Auto under a ViparSpectra V600 for 5 weeks to test it's performance, it's been lst'd, and I flipped the Bloom switched on, on Sunday evening to begin the flowering cycle as it is now at the stage where I want it to be for flowering. However, within that first 18 hour cycle it suddenly developed brown spotting on all the fingers of one leaf, within the second 18 hour period it had spread to the leaf directly opposite it, but it has not worsened any, nor has it spread to any of the other leaves yet (fingers crossed it doesn't either)...

I am doing an Hempy Bucket grow using Reverse Osmosis Water 0.00 p.p.m. - pH 6.6, I am using GHE 3 part series (Grow, Micro, Bloom), which I've used for over a decade in literally hundreds of Hempy's and never had any issues before.

Apart from these two leaves the plant is lovely and green and very healthy with no visible signs of the usual sorts of deficiencies associated with hydro grows. On weeks 3 & 4 it was fed on a solution of 1.8 ec at the end of week 4 I let it drain it to virtually empty as I normally do, to then reload it with the Flowering mix to an ec 1.4. This is the first time I have ever had this come up as an issue with this style of grow and the only variable that is different is the LED light, I have done them using both CFL's and HPS. I have grown Big Bang Autos many times so I know exactly how far I can go with the feed, because the parent Big Bangs are quite greedy feeders too...

Is it possible that it could be some sort of heat problem? I have absolutely zero experience with LED's so have no idea what has caused this, because everything was fine until I flipped on the Bloom switch, Temps are steady at 27°c in the lower half of the grow tent and 28°c in the upper, I have a 14" oscillating fan and a 4" inline fan circulating air round so good air movement/ventilation and a powerful 5" inline fan extracting the heat from the upper area of the tent. The light is approx 53cm above the top of the plant as recommended not to shock the plant etc.

No liquid has been spilt on these leaves, as feeding is done underneath and I have a specially adapted bottle with a funnel on so I can just pour it straight under the plants through the perlite, and the reservoir holds 2.7L of solution.
Below are a few photo's of the two leaves that are affected by whatever it is???

Any help/advice would be very much appreciated as I have never had anything like this before and certainly not with this method.

 

[derek420colorado]

Cal/mg deficiency are you adding any calcium or magnesium?

 

[AutoFiend]

@derek420colorado You don't need to with this method of growing when using Perlite or Perlite/Vermiculite mix under CFL's or HPS, but it would appear that, this isn't the case with LED's...Just like if you use Coco, over the last 15 years I have more than likely done in excess of 300 Hempy's and this is the first time I have ever experienced this issue, apparently it's "probably" something to do with the intensity of the LED unit, which is news to me, lol. Anyway, as I now know what it is I can get it sorted, but I'm not overly concerned as this is more about finding out how the light works and what it is capable of, than trying to produce a big yield and the two leaves it's affecting are going to be defoliated anyway as they are blocking two good bud sites. I would rather have a few teething troubles now with one plant under the light which is easier to control than have half a dozen plants and get bogged down. I've ordered some Cal-Mal from amazon so that will take care of that, and hopefully it should be a pretty straight run from here on (he says, lol), thanks for the input Derek much appreciated mate!

 

[derek420colorado]

@derek420colorado You don't need to with this method of growing when using Perlite or Perlite/Vermiculite mix under CFL's or HPS, but it would appear that, this isn't the case with LED's...Just like if you use Coco, over the last 15 years I have more than likely done in excess of 300 Hempy's and this is the first time I have ever experienced this issue, apparently it's "probably" something to do with the intensity of the LED unit, which is news to me, lol. Anyway, as I now know what it is I can get it sorted, but I'm not overly concerned as this is more about finding out how the light works and what it is capable of, than trying to produce a big yield and the two leaves it's affecting are going to be defoliated anyway as they are blocking two good bud sites. I would rather have a few teething troubles now with one plant under the light which is easier to control than have half a dozen plants and get bogged down. I've ordered some Cal-Mal from amazon so that will take care of that, and hopefully it should be a pretty straight run from here on (he says, lol), thanks for the input Derek much appreciated mate!

Yep it’s all about those LEDs I still have yet to convert(I need the heat generated by HPS and MH in my setup) but from everything I have seen on here in the last 6 years is that with some LEDs they can exacerbate some deficiencies. So it sounds like you have it handled for sure. Look forward to watching along

 

[AutoFiend]

@derek420colorado Rather than jump straight in and post a grow diary as I go, I thought it best just to keep a record as I go so that when I have finished, I can then upload it in one go, along with photo's etc. and that way it will be a better because everyone will be able to see the progress and the issues that came along and how they were dealt with and what the out come was. So hopefully, it will be interesting and all come good in the end!

 

[derek420colorado]

Sweeeeeeeeet