Derailed Already?!

After committing to the Box End Bedford Middle Distance Duathlon scheduled for 4 Sep 22 and entering, have I been derailed already? 

The dreaded Achilles pain has appeared - seemingly out of nowhere. I can only think that my enthusiasm to train, increasing run volume, has caused this problem. Last week I did record my biggest volume with a weekly total of 40k, which is not that massive really. I did a decent interval session last Wednesday too; maybe that also tipped the Achilles into stress mode. Whatever it is, I am pretty miffed. I completed the Middle Distance Duathlon mega-brick set today and struggled through. Not sure whether I should just stop preparation for September now. I'll see how this week goes but run sessions will e reduced to 2 per week.