I think it's pretty common so don't worry! I'm guessing you have at least one more experiment planned for another chapter? I didn't have a finished chapter until near the end of my 3rd year as I had huge amounts of samples to process which took two years and then ran experiments too so everything is just getting ready at the same time (not ideal!). Also one of my chapters is a very short one because the experiment I ran didn't have that many results, so even though you may not be able to publish it in a journal because of their bias for positive results, it is still perfectly acceptable to have it as a chapter in your thesis, as long as you can justify it and fit it into the 'story' of your PhD.