Look closely at the plant at the top left: that is the start of a calcium-magnesium deficiency. As calcium also affects uptake of phosphorous, you will see signs of P deficiency as well.
So how to tell if it's a Ca-Mg deficiency and not P toxicity (that locks out Ca-Mg and shows similar symptoms)? In this case, the affected plant is the biggest, healthiest, fastest-growing plant - it makes sense it is suffering a deficiency, as it has the highest nutrient demands.
Secondly, P toxicity usually first shows up as burning around the leaf margins, whereas Ca/P deficiency shows up as random "rust spots".
Mg deficiency - before it gets to the interveinal chlorosis stage (yellowing between the leaf veins) - can be seen with slight curling of the leaf margins.
Finally, I had run out of de-chlorinated water, so decided to use RO water. The deficiency showed up straight away, as the natural Ca and Mg in the tap water was missing in the RO water.
I dechlorinate my water to propagate beneficial microbes in my coco at the root zone from the organic-based nutrients.
One issue with coco is that it is susceptible to Ca-Mg deficiencies. The fibres - which usually contain naturally high levels of Na-Cl (sea salt) - will ion exchange, bonding the Ca-Mg and releasing the Na-Cl. Coco naturally bonds with free metal ions, so will lock up Ca-Mg.
Mg is instrumental in photosynthesis, whilst Ca is very important to the onset of flowering, aiding flower development.
I see a lot of Ca-Mg deficiencies on these boards that are not deficiencies at all!
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The Acids front and in the corner behind will get the chop later this week. The Sensi Stars either side probably won't be ready until the end of next week. I moved these plants around and put the left Sensi Star in the back corner, as it was getting too much light from the lower hanging frame to its left. Leaves were starting to bleach - but it's growing a massive cola!
The two plants on the very left got taken out tonight, leaving six plants still growing.
Here's Acid #3. It doesn't look very high-yielding, maybe just over 2oz. The buds are rock-hard and most of the Acids have a fruity acrid-fuel smell. I've taken a couple of samples from each plant. They'll get a 24-hour dark period before I cut them down.
