Problems with dark grains

Had my last 4 brews using dark grains turn out astringent or tannic (not sure which)

Here is what I've tried.

First 2 that went wrong I had miss read my water software and added some acid
I supposed this was the problem and adjusted for the next brew(brown ale). This too was a bit astringent, I have just started using no chill method so i figured this could be to blame.

So, next I decided to steep my grains separately and add when pitching (after a short boil with flavour hops)

Just took a sample of this brew and it is the worst yet, really harsh.

I'm a bit stumped

My water is:
Calcium 50ppm
chloride 35ppm
sulphate 75ppm
carbonates 150ppm

As I said, I do BIAB, no chill. And my grains are crushed a LHBS. I have made a few decent stouts in the past but my process has changed a bit since then.

Which grains and what styles were the last 4 beers?

1. export stout
2. brown porter (jamils recipe)
3. Brown ale(lil'sparkys recipe)
4. robust porter (jamils recipe)

My last brew I steeped 300g of chocolate malt, 230g of black malt and 450g of crystal in about 2l of water at 160f.

They should mellow with time, that said you could always try some dehusked carafa malt if your palette doesnt like the harshness.

Although 8oz of Black malt is quite a bit.

Its not that i don't like beers with dark malts, I do. Its that something has gone wrong.
There should be no need to age a stout or porter to make it drinkable.

I wonder if i steeped in too little water after rereading brewing classic styles it recommends steeping a pound per gallon.

As per the BJCP troubleshooting guides, popular causes of astringency can include overcrushing, oversparging, too high a pH (over 6.0) or too high a temperature (over 170f). It sounds like you have confirmed your crush, or at least are trusting the crush from your LHBS, and have confirmed your temp. If you are doing BIAB, I'm assuming you are not doing a sparge (dunk sparge in another pot?) or mashing out for too long at too high a temp either? In that case, the only thing left to check from this short lost of possibilities is the pH.

What happens when the PH gets too low?