I haven't grown Basil before, but does this grow very s-l-o-w-l-y?

I sowed some seeds in March which sprouted normally after 2 weeks.
Then they formed their first pair of true leaves by mid April, when I
potted up 2 of the 12 seedlings sprouted. Since then all the seedlings
seem to have made hardly any further progress including the 2 that
were potted on. The 2 true leaves have slightly expanded but that's
about all.

Is this slow progress normal for Basil?