Listen to Twistedfunk. If you have fed with blooming nutrients since the flush, leave it alone for the rest of the flowering period. Some yellowing of the older lower leaves is normal at flowering because most of the blooming ferts have reduced levels of nitrogen.
The pre-charged nutrients only work for a couple of months, depending upon how heavy you water. After all this leaching you have exhausted the charge in the soil media and your plants are getting their nitrogen from these older leaves. Don't start pouring chemicals into your soil if you don't have an accurate diagnosis of the problem. You are near the end of the flowering and don't want all that fertilizer in the soil at the end of the cycle.
I would just water normally until the leaflets in the flowers turn lighter green and then only use a 1/4 rate if needed. Your plants are doing ok, just be patient. All of these additives with fancy names don't necessarily grow good plants, sharp observation and close monitoring of signs and symptoms are the recipe for success. Next time don't use the MG soil and this will be a lot easier. You can find good instructions for soil mixes like "vics soil mix" and organic mixes it these forums or buy higher quality soils for the next grow.
Lots of people use Fox Farms or Sunshine #4 with good results.
