I know Miracle Gro isn't sufficient for micros, or at least iron, under some circumstances because I've had problems with deficiencies in susceptible container plants here, especially in cool wet weather. Plants in pots are totally dependent on what you supply, whereas plants in the ground can find their own nutrients assuming a reasonably balanced soil. With the container mixture it's hard to say what might be missing.
Might you be interested in going the tissue analysis route to find out what the plants have been able to get from the mix? I It looks like this costs $18 from Texas A & M's lab. I'm thinking item 10 although for some reason it omits zinc, you might want to ask if they can add that:
http://soiltesting.tamu.edu/fi...
The probem may only affect some daylilies because they don't all seem to have the same issues with pH and micronutrients. If you check out this image in the AHS Daylily Dictionary, these daylilies were both growing in an area of a garden where the soil pH was relatively high, but only the plant on the left (and a few others) showed interveinal chlorosis while others like the one on the right were a good green. The tissue test determined the chlorotic ones were deficient in manganese because of the soil pH being too high for those specific cultivars. There was plenty of manganese in the soil, but certain cultivars couldn't use it. I see the same thing here and I also had a leaf tissue analysis done with the same result.
http://www.daylilies.org/ahs_d...
