Indoor Yellowing and dying leaves, brown spots. Please help :(

[some_guy_]

Hello. My plants seems quite stunted and have had yellowing and dying bottom leaves with brown spots
My specs are

• ⁠Medium
Coco perlite 70/30
diatomaceous earth

• ⁠Lights
Mars hydro fc4800

• ⁠Environment details
Tent 4x4

• ⁠Strain
Mephisto

• ⁠Age
3 or 4 weeks

• ⁠Pot Size
20L

• ⁠Nutrient line and schedule
Mega crop 2 part and calmag

• ⁠Watering volume
Once every 3 days.

Ph 5.5
EC 500
Canna coco
Buffered myself

Any ideas? Thanks everyone

 

[DCLXVI]

What pH are you watering in with? What strength ppm/EC are you adding? What brand of coco did you use? Was it prebuffered or did you buffer it yourself? Have you checked runoff pH/EC? Just a couple things to start with.

Also, what are those rocks and pebbles on the top? If they aren't pH stable you could be changing your water significantly or leaching who knows what. Nutrient solutions that are a bit acidic, as it should be for coco, can probably pull something out of them. Maybe they are not a problem, just something I noticed.

 

[some_guy_]

What pH are you watering in with? What strength ppm/EC are you adding? What brand of coco did you use? Was it prebuffered or did you buffer it yourself? Have you checked runoff pH/EC? Just a couple things to start with.

Also, what are those rocks and pebbles on the top? If they aren't pH stable you could be changing your water significantly or leaching who knows what. Nutrient solutions that are a bit acidic, as it should be for coco, can probably pull something out of them. Maybe they are not a problem, just something I noticed.

• ⁠Medium
Coco perlite 70/30
diatomaceous earth

• ⁠Lights
Mars hydro fc4800

• ⁠Environment details
Tent 4x4

• ⁠Strain
Mephisto

• ⁠Age
3 or 4 weeks

• ⁠Pot Size
20L

• ⁠Nutrient line and schedule
Mega crop 2 part and calmag

• ⁠Watering volume
Once every 3 days.

Ph 5.5
EC 500
Canna coco
Buffered myself

The stones on top are for fungus gnats.
Diatomaceous

Thanks for the reply

 

[DCLXVI]

Well shoot. That was the easy stuff I could pick out and looks like you've got it covered. Only thing I know out of that list is that usually 5.8-6.2 is recommended for coco, so maybe just a touch low on the pH? I'm sure someone more knowledgeable, especially with coco, will be along to help.

 

[Heavily Medicated]

Did you possibly splash nutes on those leaves by accident?

 

[Bruce Campbell]

Did you possibly splash nutes on those leaves by accident?

<---Question #1

Other than that:

- What are the units on your EC? μS/cm? Is that just MC, or is that final (starting water + MC + Calmag)?
- Exactly how much of MC A and B are you using per gal (or liter)? What about cal-mag (and what brand)?
- What is your starting water source? RO/tap? If tap, what ppm (or, do you know how much Ca)?
- What did you use / how exactly did you buffer the coco?

If not nutrient splash, then that looks like P deficiency (or generally underfed). 500 μS/cm is a bit on the low side. But, overall, I suspect high Ca is locking out the P.

MC Part B is just calcium nitrate - it's cal-mag minus the mag. Canna coco is pre-buffered, so you should have plenty of Ca available for the plant (especially if you buffered it again yourself). And, if you're using tap water, then that's adding additional Ca.