timed release plant food mixed in the soil is a crapshoot. It can interfere with your other ferts and if too much is left when you are switching feeding schedules as for flowering, then yes, it's a bad idea. Organic supplements are a little different- guanos for example- which are released very gently compared to those chemical ball things in osmocote lol. Check in the 'organic growing' section for more discussion of that.
Okay the blister things. I think they are more a trait of an individual strain rather than m/f indicator. I've seen them quite pronounced on some females, while on others, they are almost nonexistent- the petiole and secondary growth just kinda sprout out without much ado right from the stem, with a small callus on the side (this is what you want to scrape into when you clone btw).