Its very hard to tell which you are suffering from; OTS (Over training syndrome) or normal inter-day fatigue or if it is from over reaching. This is a big part of what makes OTS such an insidious problem. Its hard to tell often, till its too late. Under normal circumstances, a couple of bad workouts in a week would not put up the OTS flag. However if you have been noticing a gradual decline in performance or unusually lingering fatigue then I’d recommend taking some action.
I’ve had to deal with the results of OTS on a number of occasions and its not fun. I’ve become very cautious and take conservative action when I see things that begin to look like OTS. I just had to deal with this when I recently started coaching a top level mountain runner who came to me with OTS symptoms. Here is how I handle this kind of situation:
1) Stairs test; Run, bound, or walk up a set of stairs that you normally (daily) climb and note how your legs feel. Heavy, dead, like lead? If they feel like this for a day but bounce back in 1-2 days then no problem. But if this dead legs feeling lingers for a few days then you’ve over reached your current work capacity and need a break from normal training. Do only recovery activities like rolling, yoga, stretching, easy swimming, walks for a few days till your legs come back. In 90% of the cases your legs will come back in a few days of this treatment and you can then resume normal training but as with any break take as many days to ramp back to a normal load as you missed from: rested 5 days? Then do 5 days of gradually increasing load and not heavy strength work during this time.
2) If the break, which for over-reaching will often be 5-7 days, is insufficient to restore your legs then you may in fact have stepped over the threshold to OTS. In this case look for some of the other OTS symptoms you need more rest and re-evalute with a stairs test ever few days.
In either case it sounds like a really bad idea to up the training next week. The plan is a suggestion not a slave master. You can only do what what your body can manage.