I have a "Build with Parameters" build that has 34 Active Choices Reactive Parameters, based off the field called ENV.  The Jenkins instance has 750, other unrelated jobs.  When I click "Build with Parameters", the Browser will spin for about 45 seconds, then it will take about another 1 minutes 30 seconds to load.  It does this in Firefox 52 (64-bit) and Chrome 56.0.2924.87 (64-bit)

If I stop Jenkins, and delete all the other 749 jobs, except this one, and click "Build with Parameters", the parameters load instantaneously.

Why would my unrelated jobs causing the "Build with Parameters" to take so long?

Attached is one of 30 fields in the job, and how its configured. They are all similar. Attached is also the current requests that sits pending for the entire 2:15 minutes in JavaMelody monitoring 

Any help is appreciated.  Thank you.