What's your percentage of exact match links in your overall link landscape?  Is it over 20% (I would assume lower, but this is the number I've been hearing)?  If so, you are probably over-optimized for your phrase.  The best action would be to change the links to either your brand, or more preferably, to a similar phrase.

However, if you have less than 10% exact matching links, I wouldn't change those at all.  Exact match is still beneficial for ranking (but I doubt it will be forever), and you would actually have some room to grow with them.

With that in mind, remember to:

• Not focus on just one keyword at a time.  Gaining 50 Exact links in a row makes it obvious they aren't natural
• Use variations of your keyword, as well as exact.
• If it's your homepage, get a bunch of Brand links.
• Keep a couple poorly optimized links in there (unless they are from high quality sites!)

Are you utilizing an unused browser, and clearing out all the cookies/history/data before checking rankings?

How's your internal linking structure?

Do a site: domain.com check to see how Google perceives your internal linking.  Are your relevant pages on the first page of your site search?  If not, you may have an internal linking problem.

To check this I used a web based program to find all the outbound internal links of each page on my website (only 200 pages).  I then transferred this data into Excel where I sorted it by page.  From here I was able to see that my most important pages had 20 less links than the unimportant pages in front of it. I then went through my website adding additional links to my important pages, using the same keywords I was trying to rank them for, until they had the most internal links pointing at them.

Internal linking is typically a problem with websites that didn't plan ahead for SEO.