I think I've found the reason for my injury; a too old, slightly bent insole in my left shoe that I use to cover my leg length difference. Took it out about a week ago and the foot is already feeling much better...
That said, this run was a bit too long for my current fitness. The first part felt great, the downhill was fine until 1/3 and then it was a slow jog down trying to mitigate the thigh soreness.
Beautiful views back to San Jacinto, San Gorgonio and San Antonio.