It most likely is stress.
Hibiscus can be real drama queens - throwing temper tantrums when they've been offended - such as planting into the ground....
Yours should be fine in a while, keep the faith!
Barb

Don't know what you're considering "good rain", but when you first plant something, rain or not, you need to water it. That's probably your main problem. One inch of rain only goes 2 inches into the soil. Brief showers or downpours don't sink in at all.

The rule is:
Water three times a week for two weeks, twice a week for two weeks, and once a week for two weeks to get them established. After that, water once a week any week you don't get an inch of rain.

I just reread your post...what kind of fertilizer did you put into the soil? The rule down here in Florida is NO fertilizer for the first 4 weeks. Time release may be o.k., but if you used granular fertilizer, it may be burning your roots. If that is the case, water very well every other day to try to get the fertilizer to leach out of the soil.

My hibiscus are doing fine now. I guess it was just the initial stress. It's January in Tampa and it's still blooming. I'll cut it back soon I don't want it to get leggy. It's a tough decision. I have seen some Hibiscus Horrors in Tampa. One question though. I pick off the spent blooms does that help them bloom?