Lizzy,
We 'blacked' our hull this year, - similar process to yours really - - sandblast, chemical wash, then a two-pack Jotamastic 87 primer, followed by two coats of Jotamastic 87.
We'd booked a dry dock and did the job myself - (because I really wanted to discover the condition of the hull in the first place, and then make sure that the job met the process spec's of the paint). We let it cure for a week before refloating.
I can say that the paint was well on it's way to being very hard indeed, and that yours really should be the same. I reckon Dr Bob's observations above are absolutely spot-on, and they would be an ideal route to start the discussions for remediation by the boatyard.