Without knowing what strain it is, it's a bit difficult to say.. autoflowers grow a bit faster, while regular photoperiodic strains can take their time..
but even if it is an autoflower, then different strains grow differently.. i have some plants (Hindu Kush) which had a bit of a slow start as well, but now they're in their third week and seem to be picking up quite a bit.. often it's just the genetics.
I think she looks good, and a dip to 19C doesn't harm them at all.
happy growing!