You should be alright for flowering simply with that HPS. Don't use "soft" white bulbs. They don't really put out a usable Kelvin for the plants. I could be wrong though, check the Kelvin rating on the soft-whites...

You want your Kelvin ratings to be about 6500K for your cool spec and 3000 for your warm spec.

I've always found that during flowering if you keep the same amount of the blue spec. you used during the vegitative state for flowering, the plant will stay more lush and lose far less of its lower leaves. And in low lighting (less lumens) conditions they will benefit from this and the flowers will become more dense. Although in some cases with some strains this is not always true. But keeping the cooler spec lights on them definatly will not hurt the plant.

I would recommend a little LST for that setup. Tieing it down will help increase lower budsite activity. I'm sure you know all about that by now.

Looks really good though! Very pretty specimen you got there.