Redirect 301 and lost pagerank. Why?

Hi everybody! In my site I had many duplicate urls with same content that were generated by joomla tags component:

1. www.mysite.com/tag/mykeyword/
and
2. www.mysite.com/tag/mykeyword/50/0/
3. www.mysite.com/tag/mykeyword/25/0/
...ad so on

I used sef advance redirect 301 to redirect urls like 2. and 3. to url 1. I did this for hundreds of urls..

The result is that in three weeks my site and many pages lost pagerank. Do you think this is temporary or I probably had a bad idea in using the redirect tool for this purpose?
I would be very grateful for any advise on the argument.
Thanks

Hard to tell. It would be best to ask tags author to fix links like that so duplicate URLs are not generated at all.