It highlights just how the breed is getting weaker with every generation – it is not just in the US, it has become a worldwide thing for all top racehorses (the only exception being in sprinting where horses can back up quickly multiple times in a season).
Your best option is probably that you could run the Kentucky Derby a week or two earlier to a point where you would have equal time between the three races (maybe three weeks each) and that might ensure the Derby winner takes in the Preakness en-route to the Belmont. The other option would be to push back the Preakness & Belmont to where you again have an equal time between the races – both option will mean a re-jig of the fixture list but moving the Derby might have the least impact on that.