RE: losing reps
could overtraining if your lifts are going down when you could lfit them previously.
has your diet changed at all or the time of day that you lift?
if i lift in the morning i'm not a scratch as strong as if i would be training mid afternoon with an extra 1-2 meals consumed prior.
some days you just have a bad day as well... weak as a kitten
so many factors involved.
chin up, take a few days rest IME and ensure your diet and rest/recouperation is not waivering.