Sad to hear you're experiencing a time of toughness and doubt! But some good advice & points for you pointed out in the thread here. My cents:
I understand this traning plan uses 2 tempo/MP ish "quality" workouts of various lengths and a slower longer one, per week. Just by that I would say key here is to get the paces right, especially at those quality workouts. Volume/ramp rate is also important & fundamental naturally, but it's a pitfall for long distance runners to look too much at mileage when discussing traning plans, and overlook the paces used and what actual adaptations in the energy systems that can be expected from whats being done by the very runner in the current state.
When determining paces, what we don't know at all from VDOT, but might get atleast a clue from 2 fresh recent personal bests from a short and a long distance (if such data is available) - is the status of aerobic and the anaerobic capacities, and how they change after a conducted block/phase of traning. If one have a low anaerobic capacity, that mean a relative fast threshold pace and high % usage of VO2max at that intensity. This mean two with the very same VDOT could get dramatically different traning stimulus in the different energy systems induced by the same traning pace. This is one of the bigger reasons cookie cutter traning plans without any metabolic testing will work for many, but will inevitably have significant percentage of fails, simply becasue it's a lottery if the adapted traning plan happend to fit you. The author don't know what's your status is at the beginning of the traning plan and thus what you actually need. And no method of checkup along the way to see if whatever what's being done is working and with good timing to whats trying to be achieved.
My guess what happend in your described case is an overreach. Probably not mainly by the mileage ramp rate in this case as some soley focus on, but that traning paces might have been too high generally. Doing alot of some kind of perceived tempo/MP pace, but that in reality might be too stressful for the aerobic system combined with the volume of traning. The great aerobic gain and the anaerobic deadaption (=performance gain in 5k and up) most usually get from that intensity might started to result in a both a lowered aerobic and anaerobic by the workouts, due to failure in aerobic supercompensation. This doesn't one typically detect in a early stage without any testing checkup, but traning is often unfortunately resumed according to the initial plan until the performance obviously is ridiculous relative to the traning load, even after some rest/taper.
Without more information I would play safe and not increasing mileage (rather lowering) and run slower paces, assuming/accepting that you probably lost fitness, and replan after this scenario accordingly.
A good general read on the topic "traning too fast", with a case example (even though its triathlon):
http://www.lactate.com/Assessment_02.html