i have found that sometimes in the beginning they can take a bit to get gowing. sometimes its climate or level of nutrients and/or PH, if you make sure that your PH is where it needs to be, and you are at a comfortable temp range for the plant along with decent level of humidity, you should be fine. it looks healthy, so that is good.
if you can make sure that all of your conditions are good and you are not over or under watering, in time it will get in line and start growing faster. perhaps also check the distance of your light to plant and make sure it is appropriate for the type of light you are using.
Best of luck to you.