Overexposed?

I recoated and re-exposed the papers.  I intentionally over-exposed them because I will use them for further experimentation.

For some reason, the images are a lot less vibrant than others I have done.  There are a lot of variables that could have caused this:

1. My chemicals are getting weaker.

2. Contamination from older cyanotype mixture or vandyke chemicals.  I was careful, but maybe not careful enough.

3. Washed for too long in water.  After researching on line I realized that I haven't been rinsing my prints enough.  Maybe I overcompensated this time?

4. I prepared the papers the night before.  I have never done this.  I noticed that the papers were not the bright green/yellow they should be, but were already turning blue...

5.  Maybe I just need to wait for them to oxidize more.  Sometimes I use hydrogen peroxide to speed it up, but didn't this time.

Update: the blue tint of the pre-exposed paper could be from a humid environment or old chemicals.  I left the paper overnight in the basement...

If I am ever going to figure this out, I need to experiment more systematically!  I am so used to trying things out on a whim.