knee soreness after parallel squat

I recently started PE2 for SLS, and everything felt ok during the actual exercise.  But now a couple days later I have soreness in one of my knees.  It hurts to put too much weight on it so I'm resting and recovering.  Is this a sign of not enough strength that I need to build up or is it a sign of improper form?  I did the front split stretch series right after the squat as well, perhaps it isn't a wise choice to do so much straight leg work after squats?  

Hi Aron,before saying something more I want to see as soon as possible your form.

I should clarify, the soreness was fairly mild and went away after a couple days, just want to make sure I'm not doing anything wrong.

I'm happy to hear the improvements, sometime quads work well! if it happens again let me know about that here so that I can give you a technical suggestion to reduce the knees effort.

Thanks! Will do!