DWC - Help needed please!

[axilotl]

A question regarding general feeding:
I change my reservoir weekly and only top up with RO water daily. This is my PPM for the last week. Measurements were always made after topping up to the same water level.

Day 1: Freshly made solution	830 ppm
Day 2	730 ppm
Day 3	620 ppm
Day 4	550 ppm
Day 5	450 ppm
Day 6 (Today)	370 ppm

First grow, but it looks like they are feeding well.

Question:

1) Should I be topping off with nutrient solution ? If so, how strong?

[axilotl]

UndergroundFarmer : Which means I should target in the lower range for DWC?

[UndergroundFarmer]

I think those recommendations are for guys growing 40 or so plants in a flood and drain system.

[axilotl]

Tersky : I think the spots from septoria from the link you provided look lighter. My spots are more brown looking. Its an LED light but I guess the effect your speaking about could be the same. I really think I didn't get water anywhere on the leaves though.

gbauto : hahaha, I think you're right. It's the first grow and I somehow don't wanna ruin it. I want to succeed Didn't think an EC that high would be required for DWC: Everywhere I searched they said, as for EC values in DWC; they should be lower than the recommendations on the packaging. When I compare it with the Tripart Chart for flowering. The table in my first post is around 25% lower. Any thoughts?

[gbauto]

axilotl, it appears to me that you're coming really close to loving your plants to death...

STOP worrying about every spot or blemish you see.
When I ran GH Flora, it always needed an ec above 2.0 for the girls to thrive in my DWC systems.
I think they are still hungry.

[Tersky]

It looks a little like either a little water got on leaves and HID was magnified by droplets and burned them or maybe leaf septoria https://www.growweedeasy.com/cannabi...-leaf-septoria. Not 100% confident in the diagnosis so I'd see what others have to say as well.

[axilotl]

NEW PROBLEMS!

Hi all,
thanks for all the support. So I extended the Veg a little bit and am now flowering since 1 week. I encountered the problem as shown in the picture below.
I am still following the nutrient schedule from my first post above. 1,1,1,1/2 (ppm around 800). Roots still look good. New growth, no rot signs.

Some of the leaves are getting these brown spots!! It's on both plants. Maybe 6-7 leaves had it.
Sprayed Neem Oil on them, not knowing if its bugs. But I definitely don't see any bugs. Cut off all the affected leaves.
Now 2 days later, after the Neem spraying, I see a few new spots appearing on other leaves.
Only thing new is, I've pruned my crops quite a bit.
Any ideas what these spots are?

[axilotl]

Thanks for the info. I'll be mixing my next batch with approx 700ppm.

[UndergroundFarmer]

Just to clarify, low ppm levels are more susceptible to wild pH swings because there isn't as much substance in the water to help buffer the effects of nutrient uptake by your plants.

[UndergroundFarmer]

It's your plants taking what they need. In mid to late flower, I always have to keep adding pH Up because of their hunger for potassium. Losing potassium from the nute solution causes the pH to drop. pH Up has potassium hydroxide as its active ingredient while pH Down has phosphoric acid. They are safe for hydro because they are also effectively micronutrient supplements. You might want to try feeding a bit heavier.

On a side note, I got Ed Rosenthal's Marijuana Grower's Handbook yesterday. According to Ed, tap water at 220 ppm is on the high side of good. All I need is to add epsom salt to boost Magnesium levels.

[axilotl]

pH instability issues:

So at 8AM, I pH'ed the larger plant back up to 6.1 (from an overnight drop to 4.5)

Now 9 hours later, I checked again, pH dropped to 5.1

During this period, nutrients dropped slightly from 390ppm to 360ppm. Water only dropped around 100mL.

Any ideas whats going on?!

[axilotl]

But isn't that the reason for using FloraMicro softwater as opposed to FloraMicro hardwater? In theory I need to still supplement CalMag ?

[UndergroundFarmer]

They should be able to handle 700-800 ppm easily (or 1.4 to 1.6 EC). For me, 800 ppm was about the heaviest feeding they could stand without showing nute burn. It depends a lot on what variety you're growing. I've got a Blueberry in late veg that can't handle more than 600 ppm. The Black Widow I just harvested took 800 ppm just fine and probably could have handled more but Bruce Banner burned past 800. I think sativas are just more nute sensitive.

[DW2]

My local water supply runs about the same ppm at a pH of 7,25 and no problems with it.

[DW2]

axilotl, I had tried using the Hydro guard before, but it did not perform like I was expecting. I have found that once ALL of the light leaks (and yes, I cover over the hydro-ton pebbles with aluminum foil!) are covered or sealed and the water temperature is kept below 70° F, the root rot will not be a problem. I have not noticed ant root damage near the ice bottles that I use to cool down the reservoir. One other thing that I forgot to mention, plastic containers need to go thru a 'curing time' before the pH levels can be stabilized. I had pH 'shifting' problems during the first two to three grows before the pH levels became normal (the levels do change as the plants take up the nutrients from the water during normal growth).