It doesn't matter whether you use a stop bath or go to Bleach III right away, you have to do it quickly, i.e. in less than 10 seconds. A bit of carry over developer is not a problem, so don't waste time pouring out the very last drop of CD, and have your bleach bottle/jug ready before you pour out the CD. The bleach was most likely in good shape after 6 rolls, assuming you had at least 1/2 liters of bleach.
While a stop bath is theoretically not necessary if you use Bleach III, here are some points why it might be a good idea nonetheless:
- Bleaching action raises the pH of Ferric EDTA/PDTA based bleaches. Higher pH leads to reduced bleach activity. Therefore carryover acid from stop bath is much more helpful than carryover alkali from CD
- Stop bath is ridiculously cheap compared to Bleach III. Therefore a gain in bleach longevity is worth a lot of stop bath.
- If bleach is no longer acidic, it may oxidize the CD and cause fogging streaks. People have had this with 120 format roll film and Tetenal's BLIX. BLIX has to operate at pH 6.5, so the problem is amplified there.