I'm pretty confident saying that those spots are Ca def and not some kind of burn resulting from lights acting on a foilar treatment (less common then people make it - I have never once suffered this effect despite plenty of foilar sprays administered under thowies, it just doesn't happen like we read on the boards all of the time). Once a Ca def occurs, there is obviously no undoing the spots on the affected leaves, but it looks to be an older problem and not a current one. As far as runoff,
it is important. There are a lot of us that will tell you to shoot for 10-15% runoff when you water, every time you water. As far as overwatering, if you saturate the soil to the point of just a little bit of runoff, getting even more runoff won't overwater them any more. The key about runoff is that it is a mini-flush - it keeps the root zone a little healthier. It is okay to go 3-4 days between watering if the soil is still holding moisture.
Sweet Lady Jane likes her feet dry, for sure, so the biggest key to not overwatering is too make sure the soil dries out pretty good in between waterings.
I am guessing that the real problems began in flowering? The plants expend a good amount of energy developing those flowers - it their last gasp, so to speak, before going to that big plant afterlife in the sky, so they are giving it everything they got. They way the yellowing is progressing on the big fan leaves is kind of indicative to an N def, but that interveinal stuff is indicative of Mg. Life is not always theoretical, so, from strain to strain, def can show themselves a bit differently and it is not always as cut and dried as we like as far as making determinations.
Cal/Mag has N in it as well, so you have covered the bases there. Since you have given them a little dose of nutes that they haven't been getting with the Cal/Mag and 15ml of iguana, if it is under feeding, you should see a stop in progeression. A stop in the form of other leaves
not being affected. The leaves that are affected can green up if it is N that they are lacking due to how mobile N is in the plant, for sure, but more important to watch in response to your recent feeding is a prevention of the same to other leaves. We don't want to see the rest of the plant doing what those few fan leaves are.
I'm really staritng to lean towards them just being under fed at this point as the major problem. If you haven't flushed them yet - do. If it won't break the bank, pick up a bottle of
Clearex, which isn't that expensive at all (one of the few
Botanicare products I endorse) and use that and run 9 gallons of water (if they are 3 gallon bags) through those bags. You only need to flush with one gallon of a
Clearex mix. A good way to flush is to use straight water until you get a good runoff, then pour a flushing agent through. Let them set for a few minutes for the
Clearex to do its thing and then flush with pure water until you have run 3 times the volume of the pot through. After that, top them off with 1/4-1/2 strength nute solution and you probably won't need to water again for 3-5 days depending on environmental factors in your grow room.
If you give me the guaranteed analysis of the iguana juice along with the weight and volume of the bottle (recommended dosage too), we can figure out how much ppm of each element it has and compare that against some known baselines of what MJ likes.
Keep us updated and post a couple more pics in a couple days so we can see how the symptoms are progressing, or not progressing, after the last boost in nutes you gave them.