Should I switch to larger pots for flower?

Putting them in 30s this late in the season and considering the current size, would be a waste in my opinion. Leaving them as they are now is probably all you will need, considering how little summer is left and the small size of your plants and the fact flowering would be commencing soon, so there won't be any real need for 30 gallons of soil due to the limited amount of growing they will be doing before flowering starts. If it were May, I would say definitely, but being nearly August, I can't see a need for 30 gallon pots. If you are really keen, 10 gallon pots would be the most suitable for this time of the year and for your situation, in my opinion. I doubt I would bother with the weirdo though, could turn out to be a waste of soil in my experience. Hope this helps, Organoman.