The average DA for a website is 30-40 while the average PA for an index page is 45-55. So you really aren't doing that bad in the overall scheme of things. Depending on the type of website and if you are concerned about ranking then I would highly recommend watching your entire website's mozRank (mR). That scales between 1 and 10 and takes into account your individual PA and overall DA.
Also take note that PA really only matters when you are focusing on improving a single page. If you focus all of your pages on optimizing for PA then your DA will also increase over time.
The Page Authority should be not lesser than 45 and the minimum Domain Authority should be 37. If both these are there accompanied with a good page rank which may be google or alexa rank then your site is a good one.
Well, if you have seen a increase over the Domain authority and the Page Authority then I would say it's a good thing because this shows that what you are working upon is correct. I would say keep working with the same, the higher will be the domaing authority means the more your domain is relevant. The lesser the DA the lesser your site will be relevant its more like how much you domain is connected with the other network. Same is the case with the Page authority higher will be the page authority means higher...... you can get a clear idea about it just by heading over to the MOZ.