Are pistils OK at this stage?

Yeah its fine, it'll explode soon ;)

Cannabis still needs nitrogen during early flowering, it is only in later stages that nitrogen needs drop off. What I have been doing for 25+ years and which works well for me, is to give grow nutrients for the first 2 weeks of flowering, or until there are small budlets/tufts of pistils formed, before changing for the next 2 weeks or so to half grow and half bloom nutrients, before then changing to just bloom nutrients through until maturity. This seems to produce the biggest blooms on plants that don't exhaust themselves to a sickly yellow colour by the time they are finished. Remember too, your plant will need every healthy green leaf she has to make the energy she needs to grow her biggest and best flowers, so if you can avoid doing any sort of defoliation, your plant will give you superior flowers due to having sufficient energy to make/grow the flowers. Hope this helps, Organoman.

I think the size is small for this age. but it will continue growing in the flowering stage as well. yes, it is OK that the little white pistils are showing up already, you need to start the transition in flowering nutrients slowly. you can do it right now or maybe after one week.