Help! What's happened to my beer?

This may be the sort of post that will generate lots of other questions, but I wondered if any of you more experienced brewers out there could shed some light on this problem for me?

I've been all grain brewing for a few years but not regularly enough to have gained a few years experience. I've had some successful brews and am now looking at water treatment to take some of the better ones to the next level, but I have tried a basic pale ale a number of times and never cracked it. Originally we had some DMS issues which we sorted out with better sanitation, longer boil times etc, but behind the DMS taste the beer had body and the flavour that we were looking for. Once we'd sorted the DMS off flavours from previous brews the initial indications were good and by the time we got to bottling the current brew, the beer was really clear and tasted like we were on the right track. We thought some carbonation and ageing would get it to where we wanted to be.

Two weeks later we thought we'd open a bottle see how it was progressing - it was cloudy and generally darker in colour (more amber ale colour now but cloudy) with lots of bits floating throughout it. The taste was more like a Belgian Wheat Beer than a traditional Pale Ale. We drank it and it didn't make us ill. We opened some others in case it was just an off bottle, but they were all the same. We had the same effect when brewing the same recipe once before.

I know that ageing may clean up certain aspects but I'm not sure why a beer would change so much when bottled or put into a barrel. Why would it now be very bitty when it was clear as a summers day at the time of bottling? Why would the flavour change so dramatically from an ale taste to a more wheat beer taste?

Is there something about the pressure that changes it when bottled or barrelled? We use WP Sterilising Powder, could it be residue from this (although we rinsed everything pretty well once sterilised)? An infection picked up at bottling (but twice in a row at the same stage creating the same effect)?

The recipe was a very simple Maris Otter base with speciality biscuit malt and London ale yeast - In case this may help to solve the problem.

Apologies for the lengthy text, I wanted to try and give as much info as possible initially.

All help much appreciated!

I'll start by asking you 2 questions. one do you know the ph of your mash of this beer and 2, you mentioned water treatments for future brews. do you know what your water profile is for this beer that your having the problem with? (soft/hard)
my first suspicions is chill haze for the cloudiness. but the free floating debris may be a by product of something else going on possibly connected to the haze or maybe the yeast flocculating or the water.  the color darkening, has got me with no idea.
ultra hard water may play a part.?   

Thanks for the advice all grain. Yes I know our water profile and we've just brought a pH meter to get accurate readings so in answer to your question, we didn't know exactly the PH of the mash for that brew, but will do moving forward.

I reckon that water hardness could be a good call so may be worth looking at RO to strip it back completely before making the profile that we want.

We'll keep trying!

Thanks Again

Try a product called 5.2 pH stabilizer. Works well for me.

I have had exactly the same thing happen with an English IPA. It was a bacterial infection.

I used to do the same as you and sanitise and rinse. But that is actually sanitising and un-sanitising. There can be very low levels of bacteria in the water which are harmless at such low levels, but give them a few weeks in a bottle of beer and they can cause trouble.

I now use Star San and DO NOT rinse. Problem solved.