in a speed slump!

I can't figure out what's going on with my pace! I think I need to start training via heart rate or something different (maybe running without looking at my pace or without a watch in general?) because I am running 45-60 seconds slower per mile than I was in January with no explanation.

Theories:

1) My new shoes--they are smaller/lighter/have less support and probably should just be worn for speed workouts and for races. I think I need to get heavier ones with more support for all of my training

2) Distance of my runs--in January and December I was consistently running 2-3 miles. Now I'm running an avg of 5-6 miles per run so I guess that would make my paces slower

3) Weight? I swear I haven't gained any weight since Jan/Dec--or if I have it is muscle! I'm so confused!!

4) Back adjustments--I started going to the chiro and learned about all these issues with my neck and back in January, but wouldn't that make me run faster if I'm finally getting adjusted? Unsure about this one

5) Mental block/plateau--It's possible I'm just thinking way too much about it and just need to relax. I'm trying to work on visualization more and mentally preparing myself for workouts and races. I've been reading this awesome book called "Mind Gym" about sport psychology and 

6) Lack of warm up/cool down/stretching--It's been awhile since I've actually done a quality progressive warm up or dynamic stretching, and I probably foam roll 1/10 runs (which is terrible to admit). 

Solutions:

1) I'm getting new shoes. I'll go get fitted for some supportive ones.

2) Keep running longer distances--eventually my fitness will get there!

3) I can't "eat whatever I want" just because I run and I need to keep that in mind

4) I'm going to keep going with the treatment my chiro suggested

5) Visualization. Determination. Planning.

6) I'll spend 10 minutes stretching each day, even if I'm not running that day! :D