The biggest issue with high RH% is, of course mold/mildew. However, mold and mildew are spores. So, if one has a sufficient amount of air circulation then spores cannot even land on your plants let alone become an issue. If you sanitize the ever loving fuck out of your grow after each harvest and you have proper air circulation, you will never see mold/mildew issues. How can you see mold/mildew if there are no spores present? And, if by some chance there
are spores present, how can they cause issues if they can't even land on canopy?
Take drying and curing for instance. Low and slow, just like aging a steak. Compare drying/curing weed to aging a steak. You can't age beef in a week, it takes 4-6 weeks. How do they prevent bad mold from infecting the beef? Air circulation. Weed is the same. Most people dry their weed in 4-7 days (give or take), then throw into jars and don't burp them enough, then wonder why their product tastes like grass. However, if you have proper airflow you can dry in 40-50% humidity for 10-14 days before putting them into jars. Again, low and slow.
As for the Mg issue.
The biggest reason for the lack of Mg is the result of one of (or a combination of) the following 3 things: 1) pH lockout or 2) the fallacy of the Calcium:Magnesium ratio or 3) insufficient mineral/organic material in one's soil.
Some excerpts from a few articles for everyone's reference.
All soils contain calcium ions (Ca2+) and magnesium (Mg2+) cations (positively charged ions) attracted to the negative exchange sites on clays and organic matter (cation exchange complex of the soil). The amount and relative proportion usually reflect the soil's parent materials. Calcium (Ca)...
crops.extension.iastate.edu
If soil calcium and magnesium levels are adequate and soil pH is acceptable, variations in the calcium-to-magnesium ratio between 2 and 8 have been shown to have no influence on crop yield.
www.canr.msu.edu
And here's some excerpts from an article about the relationship between Calcium & Magnesium in humans, which while not the
exact same as plants is still worth mentioning seeing as both are living beings.
Time to ditch the 2:1 calcium-magnesium ratio
www.newhope.com
So, in summation; CalMag deficiencies are the result of one of (or a combination of) the three things I mentioned earlier in this pots: 1) pH lockout, 2) adherring to the myth of the Calcium:Magnesium ratio and/or 3) insufficient mineral/organic matter in one's soil.
IMO, point #3 is the biggest issue as it leads into points 1 & 2. Insufficient minerals and/or organic matter in one's soil will lead to a pH lockout of some sort, either due to a lack of a pH buffer and/or a weak to non-existent CEC resulting in these nutrients being unable to mobilize as they should.
I rarely see these issues, and I believe it mostly has to do with the foliar spray I feed weekly. Epsom salts (Magnesium Sulfate) and ProTekt (Potassium Silicate), 2-3 times a week. Dolomite lime typically adheres to a 5:1 Calcium:magnesium ratio, and as most of us have experienced, a Mg deficiency tends to follow suit. The solution isn't in adding CalMag or more Dolomite Lime, but ensuring there is enough Mg in your soil or providing Mg to your plants directly in the form of a foliar feed.
Next year, when I move into my new place I will be conducting a grow journal experiment with Langbeinite (0-0-22). Langbeinite, for those that don't know, is Sulfur+Magnesium+Potassium. Loads of Potassium, as you can tell from the NPK I listed. However, my theory is that by providing sufficient enough Ca (OSF, Gypsum, Crab Meal, etc) and Mg (epsom salts) to work
with the Langbeinite that the K, Mg, Ca will all be sufficient enough. Langbeinite is water soluble, but its powerful shit as the NPK implies. So, my thinking is to try a small amount of Langbeinite and combine it with my Calcified water and Epsom Salts. However, I've found no research to confirm this as fact and I'm unable to conduct this experiment myself at the moment.