Should I Let SE's Index Tag & Category Pages?

Hi SEOer's,

Please help me out with my question:

Should I allow SE's to index my Tag and Category pages?

At first I see that it was a benefit, because I was allowing them to index my tag and category pages, because they were getting ranked on the first page for low competition keywords and getting traffic and making some money through Ads.

But the last couple days I went from getting 50-100 page views to almost nothing for a couple sites I was testing this on, they were making a few dollars a day, and now they make nothing and only get a couple page views a day.

I recently checked in 'G' my indexed pages, it is saying there is about 3 times the amount of pages that I have on the site, because it is indexing all my tag and category pages and posts.

Should I disallow the tags and categories from being indexed and give it a week or so and see if my traffic comes back or my posts get better ranks?

OR should I just wait it out let he SE's work it out and only index my posts? Because the posts, tag and category pages have duplicate content, so this is another reason they are probably hurting my traffic results.

I ask this question, because I know in the past I have disabled the categories and tag pages from being indexed and it killed my site completely, so I do not know if I should do this or just wait it out.

Thanks in advance for your experienced answers and suggestions.

Regards,
Kyle