OK we are beginning to see a pattern here. It looks like all of the issues are happening down low on the plant while up high and new growth is still fine. If you have looked them over carefully, we can rule out bugs, and you say you water/feed from the bottom so that rules out splash damage (that and the fact that it is occurring on multiple plants). So what you need to look at now is which elements are not very mobile in the plants, and which elements are mobile as the lack of one or more of those elements will cause damage down low but not up high.
Also, with the mobility question comes the idea that with some nutrients, if the soil isn't providing it, the plant will rob the needed nutrients from the lower parts to give to the upper parts where the flowers are. Also, notice that the issue didn't show up until they began flowering.
Just from the look of it, I am thinking that you are lacking in available micro nutrients. I am thinking either calcium, or manganese. However, potassium deficiency can also present this way as well. This still leaves us with several possibilities. It may be that the organic nutrient line isn't able to supply enough of what the plants need, and/or the microbe herd in your soil isn't strong enough to process the nutrients at a rate that is needed by the plants at this point. OR, the pH in the soil has gone way off the rail and has interfered with both absorption and microbe activity.
