I would firstly suggest getting some site reviews, i.e post your sites on as many gaming affiliate forums as possible. See what people come back with, if there is consistency in some suggestions, perhaps try changing the site etc.
Also, take a good look at all your on page stuff, i.e is your content of good quality, and are all the meta details as good as can be.
Now, What is your main market for the three sites? Have you Geo-targeted in Google Webmaster tools?
Also, what are you doing with regards to SEO?
A quick look at heaven4gamblers.com shows that you have no organic keywords, in any territories. My software may be innacurate, are you aware of any that you are ranking for?
Heavenforcasinos.com appears to have just one keyword, “mansion casino review” with a position of 260.
In regards to back links, you have just 415 back links to heaven4casinos.com from a total of 39 domains. Also, it would seem that you don’t have meta descriptions for a large amount of your pages. Some also have very long meta titles. I would look at rectifying this as soon as you can. Also, try and look at building gradual, natural back links Press releases can be a good way of going about this.
Heaven4gamblers.com has 435 back links from 39 domains too. This doesn’t have as many errors as the site above, but does need some good quality, natural looking, relevant links built to it.
Also, heaven4gamblers.com seems to have a large amount of links on the homepage, dunno whether these are internal or third party links, but it might be doing more harm than good.
Hope this helps in some way