Hungry or sick - hydro experienced help

[Reallybman]

Hi all - this is my second grow. Previously did two plants in 5 gal DWC. That grow went really well. Battled some root rot early and recovered.

Current grow: 11 plants in a 20 gallon RDWC. Roots are healthy, lots of air stones and aerator nozzles. About 3 weeks into veg. About half of the plants are showing spots or something on their older, huge fan leaves. See pic. Not finding any bugs on my sticky pads.

Using floragrow 3 part nutrients. Ph around 6, adding hydro guard for root health and alight dose of calmag as my tap water seems to have enough calcium on the last grow. I did a 24 hour flush to make sure it wasn’t nutrient lockout. Not noticing a change. Ppm is about 800 when I change res water. It’s down to about 325 now as I add just plain, ph tap during top off.

Grow room is 4x8, two Mars Hydro TSW 2000w LED. Temp is around 70, probably RH of 45%

Any help appreciated. Topped the plants after 6 nodes, at the fourth node.

 

[Nate_in_AK]

http://loudclouds.co/wp-content/uploads/2016/07/marijuana-deficiency-chart-jorge-cervantes.jpg

I'm going to guess Calcium deficiency.

 

[Oldguy71]

Hungry. You want your ppms to stay about the same over the life of the reservoir. If your ppms drop your plants want more food. If they go up they want more water. I’d raise the nutrient level like 100 ppm every couple days until you find that spot

 

[Nate_in_AK]

Hungry. You want your ppms to stay about the same over the life of the reservoir. If your ppms drop your plants want more food. If they go up they want more water. I’d raise the nutrient level like 100 ppm every couple days until you find that spot

Great advice. I started tracking my pH and EC/PPM readings several times per day, as well as recording the water level at least once per day. The balance will change over the life of the plant, but ideally you want to see pH and EC stay the same while the water level drops. Rising EC is caused by the plant drinking more water than nutrients. Falling EC is caused by the plant eating more than it drinks.

Keep us posted on your progress, I think your plants will be fine once you get the feeding balanced.

Every strain seems to have different feeding requirements, so it's always a bit of a dance.

Good luck!!

 

[Reallybman]

Thank you for the help! It’s stressful because some plants are perfect. See pic. About half have some spots and half have zero spots. I’ll up the feed gradually. I track PPM and PH more than EC. I don’t really understand that one...

 

[Nate_in_AK]

Thank you for the help! It’s stressful because some plants are perfect. See pic. About half have some spots and half have zero spots. I’ll up the feed gradually. I track PPM and PH more than EC. I don’t really understand that one...

PPM and EC are just two different ways of reporting estimated nutrient density.

EC is Electrical Conductivity. Depending where on the planet you live, PPM is calculated by a factor of EC. In the USA PPM = 0.5 * EC.