Week 2 of Veg. Plants very small

Size varies a lot based on Strain, Light, soil and water. Mostly Strain. I have had some plants start off growing like crazy and others just take their sweet time. I do know that once the roots hit the bottom of your container/pot it will start to shoot up quickly. We start our seeds and little clones off in just a small 1"x1" cube. Once the roots are showing they move into a 4" pot for about 2 weeks where they start growing up quickly before they get moved into 1 gal pots. Then 2 weeks later into their final 5 gal pots. I know some prefer not to have the stalled period that happens when you transplant, but I like big plants and always try to get them to at least 24" tall for indicas and 36" for sativas/hybrids, just my personal preference. Yours looks healthy, so just give it another couple of weeks.