Roasted Barley/Pale Chocolate Astringent

I brewed a coffee porter and bottled it a couple weeks ago. There is an astringent, almost sour bite to it. I don't believe it is an infection; It is more like the underlying bite that most porters have, just very pronounced. I'm curious if 1) my grain bill is just a bad recipe and 2) will the bite from the roasted barley and pale chocolate mellow out after a couple months in the bottle? Here is my grain bill:

75.7% Light LME 7lbs
10.8% Crystal 60L 1lb
8.1% Pale Chocolate 250L 12oz
5.4% Roasted Barley 8oz

What is your water like? Roasted grain drop the pH, which is why they were often developed in areas with high carbonate water (which buffers the acidity). pH is a bigger issue in all-grain brewing, but I've found some chalk or baking soda to really improve the smoothness of my dark beers.

I just posted a thread asking about the downsides of squeezing the grain bag to speed up the straining process. I was told it is a no no and it extracts alot of tannins. Tannins give an astringent sort of flavor. Did you squeeze the grains?