10# (13 pints) frozen blueberries that were washed, brought up to a boil, and mashed (Aldi's $1.29/pint)
5 qts. boiled, non-softened, city water
7 1/2 tsp acid blend
2 1/2 tsp pectic enzyme
Just over 1/4 tsp K-metabisulfite (potassium metabisulfite)
I followed the previous blueberry recipe to a tee.
On the first day I added a slight amount of water and left out the sugar, nutrient, energizer, and yeast until 24 hours later. It is a type of fruit "liqueur". The higher volume of pectic enzyme to water will allow the pectin in the fruit to break down quicker.
Instead of a full campden tablet for sterilization, I also used the K-metabisulfite. Campden is often times made of sodium metabisulfite which will add sodium and can apparently impart a slight off flavor in the wine. I used a whole one in the 2010 batch, but 1/2 is all that would probably be needed anyway.
Due to the following info from www.winepress.com, I waited until 90 degrees F to add acid blend, pectic enzyme, and K-mertabisulfite:
Joel, somewhere I have the exact temperature at which enological pectic enzyme becomes 100% ineffective, but unless I were extremely lucky I could search through books all night before finding it and I'm not going to do that. All I recall is that it is slightly over 100 degrees F and believe it is about 80% effective at 80 degrees and completely effective below 65 degrees. The 80% at 80 degrees correlation just jumps to mind and I have always used it.
So, my guess is that the original enzyme was cooked.
The other issue you raised was adding pectic enzyme to a fermenting must. That is generally thought not to be a good practice. Once yeast are pitched, you shouldn't add anything except fermentables or possibly nutrients until fermentation is done or very close to being done (for example, an s.g. around 1.010) -- no pectic enzyme, no acids, no fining agents.
It is unlikely you'll have a problem, but if your yeast just quit prematurely it might be because they really don't like their environment chemically changed. But if fermenting vigorously, it is unlikely they will be affected. Still, in the future be patient and let your must cool to room temperature before adding enzymes of any kind (there are many enzymes identified for enological purposes).