Any risk for owning two sites on the first page targeting same phrase?

[Gissit]

I own a couple of sites that used to rank first page (until mid June) for the same term (and within the first few pages for a load more). One of the sites has recently taken a dive and I am trying to find some reason.

Site 1 is a four or five years old ecommerce that sells product. I got out of this a couple of years back and so I lease the site to another dealer now.

Site 2 is a 2 1/2 year old classified type site for people looking for similar product to site 1.

Both sites run on the same server, both are in my WMT account and both domains are registered in my name. Any links between the sites are nofollowed.

Site 2 is a far stronger site and is clean with no funny stuff. Was ranking top 10 for a large range of generic searches in the topic and a whole load of long tail searches. A search for [site 2 domain name] (without tld) lists it at the top with sitelinks. A search for [sitename - site topic] and it is burried way down behind a whole load of sites that mention it (including site 1, seems google does not ignore outbound anchor text on a nofollowed link). Some terms still put the site on the first page but lower than previously. Some very specific (and non-competitive) terms have gone altogether

I can see why this might cause some sort of filter / penalty and am thinking of shutting down site 1 but thought I would post my thoughts here first to see if anyone has experience of this.

[tedster]

If both sites were ranking well on the same phrases, PLUS there is common whois ownershiop (and possibly a similar coding footprint) there may be some possibility of a penalty or filter. But i'm not sure that's likely.

There are many reasons that a site might take a sudden dive after a long period of success - and common whois ownership on its own, is not likely to cause a problem, especially since you've always been straight about it in Webmaster Tools. Also, you're taking measures NOT to use one site to boost the other in Google Search, so I kind of doubt this is the problem.

I've seen mysterious drops like this show up and then go away after a few days, or maybe a couple weeks. But then there are others that just hang in there. It would be good to give your site a through going over, such as I just recommended in another thread [webmasterworld.com]. Especially look for liabilities in the duplicate url area, and see if there is any potential for competitive sabotage [webmasterworld.com] as well.

[Gissit]

tedster
The sites are both in my name in whois but the code is very different with site 1 being a gpl cart and site 2 handcoded php/sql.

The whole story is that this happened a few weeks back on 11 June and the site went for a week and then returned again. I thought it may be something to do with the thread on 4 June issues and that I was running a bit behind as usual. I just put it down to a glitch until it went again last Friday and now I am thinking it is personal.

I'm pretty confident that it is clean but there are always areas that may be shades of grey.
For instance:
I have a list of businesses and links that are subscribers - does that make these paid links? It's easy to get paranoid.
I have database content pages for 'All Widgets' and 'Red Widgets' 'Yellow Widgets' etc and so there is a bit of duplication between the 'All' and other categories.
There are 100 items on a page with a couple of links on each for user interaction. The links are nofollowed as there is nothing there for a search engine but if they still count as links then I have far too many on a page.
With all the nofollows going on am I over optimising?

The more I think about it the more of these type of questions come up. I think I'll go get a beer!