Normal peak flow readings but low FEV1

I was diagnosed with mild asthma years ago, but occasional use of albuterol seemed to keep symptoms in check. This summer I started experiencing chest tightness and coughing. About a month ago, my doctor put me on symbicort and singulair. Because I didn't perceive much change in symptoms, I bought a digital peak flowmeter to try and get a sense of what is going on. The meter also measures FEV1.  

My peak flow readings have usually been normal (within the reference values I've found on multiple web sites), but my FEV1 readings seem low. My highest FEV1 reading is 2.04l, but it is generally lower than that. I am 40 year old female and I am 66 inches.

Since the peak flow values are OK, should I be concerned about  the FEV1 readings? Why would one measurement be normal and the other be low?  

Many thanks in advance for any insight you may have.