They all work fine for me?
You do have some syntax errors, but nothing that looks dangerous.
For completeness you should end conditions with a $ to indicate a complete match. So this...
HTML Code:
RewriteCond %{HTTP_HOST} ^eastsidechiro.net [NC]
Shoud be this
HTML Code:
RewriteCond %{HTTP_HOST} ^eastsidechiro\.net$ [NC]
You will see I made another change. When doing RewriteConds a dot means any character. You should replace it with backslash-dot to specifically restrict the match to a dot. The following condition you used had it right.
HTML Code:
RewriteCond %{HTTP_HOST} !^www\.eastsidechiro\.net [NC]
RewriteRule ^(.*)$ http://www.bellevuechiropractor.com/$1 [L,R=301]
However, the above rule has an exclamation mark to start the rule (and is missing the final $). I've never used that option but it technically means a negate. i.e. Anything that does not match this. As the previous rule to it has the same condition without the negate, this condition is saying, for any other domain. It's rule says pass on the same path by using the $1 in the destination.
Lets have a look at what's happening at the moment:
HTML Code:
http://www.eastsidechiro.net/ -> http://www.bellevuechiropractor.com/
http://www.eastsidechiro.net/index.html -> http:// www.bellevuechiropractor.com/
http://www.eastsidechiro.net/fluoroscopy.html -> http://www.bellevuechiropractor.com/motion-xray.html
http://www.eastsidechiro.net/fish/ -> 404 error with no redirect *****
http://eastsidechiro.net/ -> http://www.bellevuechiropractor.com/
http://eastsidechiro.net/index.html -> http://www.bellevuechiropractor.com/
http://eastsidechiro.net/fluoroscopy.html -> http://www.bellevuechiropractor.com/ *****
http://eastsidechiro.net/fish/ -> http://www.bellevuechiropractor.com/
I've starred the ones I think are wrong. I'm note sure why it's currently happening like this. Have you made changes?
I'd actually re-thing how to do this.
It seems you have several pages from the old domain that have now moved on the new domain. Deal with them first, they fix the domain for you anyhow. So put your Redirect 301s first in the list. Then do the domain switching rules. For those I would pass on paths and query strings so you can still track when people refer to bad urls. You can then add more Redirect 301s to deal with those issues. I think a template for your domain redirect should look like this:
HTML Code:
RewriteCond %{HTTP_HOST} ^www\.eastsidechiro\.net$ [NC]
RewriteRule ^(.*)$ http://www.bellevuechiropractor.com/$1 [R=301,NE,NC,L]
This basically says, just change the domain name and leave the rest as is. The path is left in tact because of the $1 and any query string parameters are passed on by default. Your index.html issues should be dealt with by some Redirect 301s you place before these.