Yellowing and dying leaves not from lack of N

Veg stage is over and flowering stage has begun. Most of my lower leaves on about 2/3 of the plants are yellow(ing), and some are browning and dying completely. I know my nitrogen is good, there may be even slightly too much as the top leaves are dark green and a nitrogen test showed adequate levels. A few leaves have dark edges and stems with slightly lighter green on the inner leaves almost turning yellowish, also some of the petioles are purple-ish on the underside(P deficiency?). I can only think that it may be a lack of Sulfur or some other micro-nutrient, may also be potash but that level also seems adequate. I feed with blood meal originally, then two doses of 10-10-10 before symptoms appeared. And Last week a cut down water soluble 18-18-21 nute in hope to fix. pH tests are all over the place ranging from 6-7 with an average of 6.6 so the potash should be available. Note: outdoor bucket grow. The 18-18-21 was applied after I noticed the problems. I use river water with a neutral pH and no Sodium to worry about.

way to test your nitrogen content "nitrogen test"??? Please enlighten me...... Because yellowing starting at the bottom of the plant is classic sign of nitro def, and your plants will gobble up a ton a nitrogen the first 2 weeks into flowering..

Attached pic, leaves are taped onto the paper. And the nitro test kit said adequate, if anything there may have been too much as the tops are dark dark green, but i understand you point about it eating it up which is why i applied that heavy nute. take a look at this pic,some of the other leaves are all yellow and dying, but not a majority.

Nitrate - Ammonium is found in both inorganic and organic forms in the plant, and combines with carbon, hydrogen, oxygen and sometimes sulfur to form amino acids, amino enzymes, nucleic acids, chlorophyll, alkaloids, and purine bases. Nitrogen rates high as molecular weight proteins in plant tissue.
Plants need lots of N during vegging, but it's easy to overdo it. Added too much? Flush the soil with plain water. Soluble nitrogen (especially nitrate) is the form that's the most quickly available to the roots, while insoluble N (like urea) first needs to be broken down by microbes in the soil before the roots can absorb it. Avoid excessive ammonium nitrogen, which can interfere with other nutrients.
Too much N delays flowering. Plants should be allowed to become N-deficient late in flowering for best flavor.
Nitrogen Deficiencies
Plants will exhibit lack of vigor, slow growth and will be weak and stunted. Quality and yield will be significantly reduced. Older leaves become yellow (chlorotic) from lack of chlorophyll. Deficient plants will exhibit uniform light green to yellow on older leaves, these leaves may die and drop. Leaf margins will not curled up noticeably. Chlorosis will eventually spread throughout the plant. Stems, petioles and lower leaf surfaces may turn purple.