Get some recovery - you needed it before JK and even more now. The last thing to do now is to carry on flogging yourself, you're tired (for whatever reason, overtraining, work, illness) so let your body recover - its when you are resting that your body gets fitter.
Maybe you felt tired cos you were shifting? Crude scaling up of times (5.1 ->5.9) suggests your time was equivalent to 30:0x for the long leg.
A squad coach from the Deeside area once told me that when you're running hard you always feel tired...
perhaps a mixture of both. relay was the best one physically but it was also the flattest and i've felt good intermittently on the flat.
some hill reps and strength work should turn it around!