My plants are dying and no one knows why. I need help!

[Wolverine97]

Burned 'em, then compounded the problem with the Sea Crop and silica. It's probably not worth trying to salvage them, hard as that is to accept sometimes.

 

[Lester Beans]

I do not see evidence of fungal disease.

 

[TanzanianMagic]

Hi guys,

I'm new here and desperately looking for help. I've done a lot of research and talked to several people, but I haven't found a solution yet.
I'm having the same problem with my mother plants and the clones I took from them.

My mother plants are almost 4 months old in veg stage. Strain: Glue #31 compound genetics.
30 days ago, they started to show burns on the tips of the upper leaves. These burns spread throughout the leaf until they kill the entire leaf.
The new leaves grow smaller and smaller until the problem takes over the entire plant and it dies (I've already lost 5 plants in the same way).

I uploaded some photos so you can better assess the situation.
Does anyone have any idea what's attacking my plants?

Watering and Grow Room Information
Sealed room
Coconut fiber soil
2 gallon pots
Strain: Glue #31 Compound Genetics
Input EC 1.4 / Output EC 1.8-2.2
Input pH 6.0 / Output pH 5.9-6.5
Runoff 30-40%
Watering once a day (0.5L to 1L depending on the plant)
PPFD 350-450
CO2 500-800ppm
Room temperature 25-27°C / 77-80°F
Room humidity 60-70%
Watering solution: plantprod calmag 13-0-13 (1g/L), ppmj grow (1g/L), silicate (0.4g/L), seacrop (1mL/L) and H2O2-hydrogen peroxide (1mL/L)

Tkx a lot!

1. I'm not an expert on sealed growrooms yet.

2. The output of the EC is high and suggests a buildup of unused nutrients in the coco coir. Which would suggest this is the reason the plants look crispy. Reduce the EC to 1.0 max during vegging. Also, if you're using coco coir (bagged), you should also start with coco specific nutrients - Canna, Plagron, Biobizz.

3. The humidity is relatively high, and may be interfering with the respiration of the plant.

4. Watering once a day is way too often. Only water when the coco coir is dry in the morning.

5. The pots are too small. 1 gallon per expected foot of growth, minimum. If it's 5 feet, that's 5 gallons minimum.

So in short: less frequent watering, lower EC, bigger pots, using different coco specific nutrients. Also bagged coir has much fewer issues than bricks.