Help! My site is no longer ranking, but did not get penalty

My website (anti-agingweb.com) was doing quite well in the rankings and had a growth rate of about 60% each month. That suddenly changed on 27 April when I noticed a 90% drop in rankings. Ever since then my site has all but disappeared from the rankings and hardly receives any traffic.

I wrote a reconsideration request but recently received a notice that I did not violate any guidelines and that I was not penalized. I'm basically left to figure out myself why my rankings have dropped.

It seems then that perhaps the new algorythm is to blame. But can that really cuase a loss of traffic of more than 90%?

Also why was it caused? Here is a few things I noticed. I noticed that a lot of the pages that were indexed are from an image gallery I recently added (next gen gallery). Although I only added a few images it seeemed to have generated a lot of pages in the index. eg. anti-agingweb.com/over-40-fashion-gallery/?ngg-pid=10&r=80

Another thing I noticed is that there are quite a few indexed pages for my subscription plugin: eg.: anti-agingweb.com/comment-subscriptions?srp=13&sra=s

I wonder if all these pages could be considered as 'low content pages' and therefore the rest of site is undervalued.

In an attempt to delete these pages from the index I have added these commands to the robots file:
Disallow: /nggallery/
Disallow: /nggallery
Disallow: /over-40-fashion-style/?
Diaallow: /nggallery/post/
Disallow: /comment-subscriptions?
Disallow: /over-40-fashion-style/
Disallow: /wp-content/plugins/sexybookmarks/

However, a month later a lot of the pages mentioned above are still indexed.

Does anyone have a clue why my site suddenly doesn't rank anymore? Any ideas on how I could solve it? Am I doing something wrong that I'm not seeing?

Any help much appreciated!