seems rather odd that both hulls suddenly start doing this at the same time.... something has caused the failure or its related to another issue not yet discovered
Have you checked the rudder case pintels where they attach through the transom ?
I know through lots of experience that the lower pintel is under a lot of sideways load compared to the upper pintel, I've actually had the mounting bolts sheer on a couple of occasions and as a result the holes that they passed through became oval in shape and allowed water in.... certainly pay to check that area
I solved my issue by going to larger bolts in the lower pintel but left the upper pintels as they were..... the uppers are 3/16 while the lowers are now 1/4, since that change I've had no further issues.
A simple way of testing is to.....
fit a push-bike tyre valve to a hatch cover (use a spare cover for this)
use a push-bike pump to add some air pressure to the hull, don't use an aircompressor and a car valve, you could induce a rush of air that could in theory split the seams on the boat.
To give you an idea, 3pound of pressure will be enough to rupture the hull
A push-bike pump wont supply a rush of air and you wont get the pressure needed to do damage
get the chief cook n bottle washer (or who ever is around) to run a tea-towel that's been soaked in soapy water over all the possible places you think a leak is coming from.
You'll soon see a mass of bubbles in the soap-foam where the air is escaping from, if needed use a pastry brush and a cup of soapy water to 'fine tune' the exact spot the air is coming from
I find it odd that both hulls fail and water is entering via a repair, I tend to think its the pintels and its an easy overlook, the riggors of racing and a few hard turns or reefing on the tiller will load up the lower pintels. to a point where they can become loose or in my case, actually sheer the bolt...
good luck with the hunt