thats the typical growth I get off of my seedlings, usually a bit more. I recommend transplanting soon, maybe when you start to see five finger leaves.
also, make sure you aren't over watering. that slows down growth a bit at this stage.
Def normal for two weeks... About a month into veg im only @ maybe 7-8 inches... But i use MH for veg... Not sure what your light source is... For Now... Instead of straight pouring water in get yourself a spray bottle and spray the soil to achieve moist soil rather than soaking it