I edited your post to include the numbers for each of those books, just in case there was any confusion.
I wouldn't necessarily say that all of those books were filler, but I suppose that depends on your definition of filler. Besides, even some of the books that clearly didn't affect the plot at all were great fun to read.
I did quite enjoy The Forgotten #11 as it had time travel (something I nearly always enjoy) and the Amazon Rain forest (a place I've always wanted to visit).
The Unknown #14 was funny. I liked how they made it look like humans might actually know about aliens, but it turned out to be an old Andalite toilet! I also thought it was hilarious when they pretended to be Fox Mulder, Dana Scully and Cindy Crawford!
The Warning #16 was cool because of all the security guarding the mansion and the fact that Jake went Rhino and trashed the place! It also mentioned the internet for the first time.
I liked The Extreme #25 because I like Marco books and the plot was interesting.
The Experiment #28 was funny because Ax got a TV!