Areseneo? Come on man no need for petty insults...
I don't see anywhere in your little link that discusses calyxes turning yellow. Are you just overlooking that? It's quite clear in the pics that it's more than the leaf. So until you find me something that details what deficiency manifests itself on the calyxes don;t act like a dick, because until that last post I thought we having a simple discussion. So maybe you thought we were having a "tug of war", but it's not at all how I'm going about this, I'm not trying to win... What if it is just simple albinism?
There's more possibilities than deficiencies.
Either way, hypothetically, let's go with Fe and Mn deficiencies:
Iron deficiency:
- Pronounced interveinal chlorosis similar to that caused by magnesium deficiency but on the younger leaves.
-Leaves exhibit chlorosis (yellowing) of the leaves mainly between the veins, starting with the lower and middle leaves.
Fe is unavailable to plants when the pH of the water or soil is too high. If deficient, lower the pH to about 6.5 (for rockwool, about 5.7), and check that you're not adding too much P, which can lock up Fe. Use iron that's chelated for maximum availability. Read your fertilizer's ingredients - chelated iron might read something like "iron EDTA". To much Fe without adding enough P can cause a P-deficiency.
Manganese Deficiency:
Interveinal chlorosis of younger leaves, necrotic lesions and leaf shredding are typical symptom of this deficiency. High levels can cause uneven distribution of chlorophyll resulting in blotchy appearance (necrosis). Restricted growth and failure to mature normally can also result.
-Mn gets locked out when the pH is too high, and when there's too much iron. Use chelated Mn.
here's a chart as well:
http://www.weedfarmer.com/cannabis/tables_guide.php
I can kind of see why you think it's one of those deficiencies...
Quick Breakdown:
It could be a Fe def. if his pH is off, or there is too much P which will will cause a lock-out.
If it's an Mn def. it's could be due to a high pH, or too much Iron.
So according to "any reasonable explanation or source about what is causing the problem", fix your pH, and make sure there isn't too much P to cause a lock out.
Hopefully, Serapis, you realize that just because you disagree with someone you don't have to call them names.