HELP! What's causing this?

[damanc]

I've had this problem for a couple weeks but I'm growing AK-47 and the leaves are turning yellow through the bottom half of the plant. There's also some brown tips and a few leaves that are starting to curl down near the tips and a couple leaves with small brown spots starting near bottom of plant. I'm growing in Fox Farm Happy Frog soil and using Fox Farm Grow Big nutrients every other watering. This is only my second grow ever so any help would be appreciated. Here's some pics...

[Gator]

Are you using cal- mag

[damanc]

I wasn't using Calmag but I just started using it yesterday. I'm hoping that's all it is.

[Bluey]

Couple of things going on with your leaves there.

Loss of pigment on some leaf edges.

What appears to be burn on the tips and some leaf edges

Loss of pigment between the margins.

First thing to look at is your pH. What pH are you giving them with the nutes and what pH are you giving without the nutes and type of water? Are you varying the pH to suit the soil range for that stage of growth? What parameters?

Are you measuring the EC or PPM of the feed?

I know nothing about that soil or the nutes you are using so someone can jump in on that?

Watering frequency and how iften do you run off and how much?

Brown spots (rust) and loss of pigment is normally a calmag deficiency, common as in coco, but I think you may have other shit going on but not sure what exactly.

Temps and RH (VPD if you know it)?

Edit. Light levels? Reducing light till the problem worked out will often help.

Edit #2. The calmag deficiency is not likely being caused by a lack of calmag. Need to determine the cause. Likely pH or watering practices.

[damanc]

Thanks for the reply.

1. I will have to check the PH. It's been awhile since I checked it but last time I did it was about 6.5 will definitely check it.

2. To be honest I just got a TDS/EC meter and will check that.

3. Next feed I think I will give less nutes or maybe do a flush before that. What do you mean by doing a runoff?

4. I water every 3 to 4 days and about a half gallon each time. I'm growing in what I believe is suppose to be a 5 gallon fabric pot.

5. Right now with lights on RH is 59 and temp is 77°F and VPD is reading at 1.3. This is the numbers it's usually running at during the day give or take 1 or 2 on the temp. At night with lights off the temp drops to the upper 60's (66,67,68) and RH is the same around 59 or 60. The temp drop at night brings the VPD down to about 0.9.

6. I'm using 2 Viparspectra 100w LED lights so 200W together. The book that came with the lights says in vegetative stage to put light 16 inches above top of plant between 75% and 100% intensity. I have it 16 inches at 100%. But the problems are happening in the bottom half of the plant or bottom half of the branches. So I figured if the lights were too close or to intense it would effect the top leaves.

[GrowNinja]

Just chiming in. Runoff would be watering until the water leaks from the bottom of your pots
And how many times have you given water until u see water coming out of the bottom, also how much water do you have coming out at a time.