I live in a similar clime and yours are acting the way mine always have - it's just not warm enough for them to bloom a lot. You'll get a few blooms here and there, but nothing like in the summer. They go somewhat dormant, so fertilizing won't help.
Barb

Brien, I'm assuming your hibs are in the ground, right?
I have 5 tropical hibs and 1 hardy..(No matter what I did w/the hardy it'd never bloom) but I feed my tropical hibs yr round.
I use a special hib food bought at either www.stokes-tropicals.com or www.plumeriapeople.com This fertizier is worth it..If your hibs bloomed this time before then they are capable of flowering in winter. Give this food a try..It's only for hibs, no other plants..Toni

That's funny...I have the opposite problem...mine bloom like crazy in the winter and hardly anything when it's hot.

I thought mine were dead by the end of summer i just about gave up on them and once it cooled off, they grew about a foot and the blooms are magnificent. Mine have double flowers. maybe different strains have different preferences.