A few months ago i did a London pride from GW book and kegged it (I normally bottle). I used nottingham yeast on that occasion. I was very impressed with the clean no off flavours (to my taste anyway) to the brew. So i did another batch of London P but this time used wlp 002 and bottled it. I mashed a tad lower temp too, to try a less bodied brew. After ferment and a week in the warm place to carbonate in the bottles I had a bottle and was extremely happy with the flavour, mouth feel, maltyness, carbonation, hops - everything really. Mash ph was good too and there was no harshness to the beer just clean flavour. I was chuffed to bits!

2 weeks later the beer seems to have lost it's freshness/clean taste. It now seems like harshness to the brew is creeping back in (as if my mash ph was too high). 3 weeks later and no improvement. When i had my first bottle I thought it was only going to get better. Doesn't seem to be panning out that way.
Storage/aging is in a dark room at about 10-12 degrees. Should be prefect.
Whats going on as generally all my beer gets better with age. Should I just keep waiting - or is some beer just better really green.