Zill, though fungus gnats are said to be harmless, but annoying, they will devour roots/leaves.
Is your hib growing outdoors or in a pot? Sounds like the soil is being kept too wet..
Fungus gnats love wet soil and dry air..If kept in a pot, allow soil to dry between waterings..if outdoors, then when hosing, aim at upper foliage w/wetting soil, unless soil is dry..Good luck, Toni

Thanks for the suggestion, Toni. The Hibiscus is outdoors, and I do water the area a lot (it's by the mint). I'll try cutting back on the water and, hopefully, get a bushfull of perfect hibiscus. Thanks again.
Zill

The young of fungus gnats can damage roots. But neither the young nor the adults eat leaves.

More likely the through-and-through holes in the flower buds are due to a chewing pest such as a recently hatched caterpillar.

jean:
Thanks for the suggestion. The damage does look as if done by a "chewer." No further holes -- perhaps it's passed on.
Zill

I had the same problem last year - and it was from catepillars. I checked my plants often and flicked the little buggers off. They also hit my passionflower vines, but these I let go - the butterfly's they turn into was worth a little damage and the vine had so many leaves, I didn't mind some damaged.
I think the caterpillars were hairy, black and brown/red stripped. They did hit in the late summer though, not in the spring.
Barb

Thanks, Barb. I suspected caterpillars, especially with all the moths we've had in Phoenix this year. Every morning I've examined the plant, but found nothing. (Shouldn't complain about that!). Probably just a passing cat. You grow plants, you expect holes -- it was the perfect quarter inch tunnel, side to side, with no other damage, that was odd. I'll probably never know exactly what it was...
Zill