[RWP] Why Would One Soft Synth Follow Reaper's Tempo and Another Not?

[Indigo]

I noticed that the VST synth Tone Two RayBlaster was following the tempo 
of my midi keyboard; for its arpeggiations,  and not Reaper's project tempo.
In Project Settings, I changed the BPM from 120 to 90 and placed a check 
mark on a field called follow Tempo...and RayBlaster soft synth now 
follows Reaper's tempo, but another soft synth; Sylenth1 is still 
following the midi keyboard's tempo.
Surely settings made in the same Reaper session will apply to any 
inserted VST synth.
Sylenth1 is so closely receiving messages from the midi keyboard that 
the arpeggiation hold button on the keyboard causes Sylenth1's sounds to 
hold, and not decay.
Is there any other setting in Reaper's Project settings that might force 
Sylenth1 to follow project settings and ignore some of the unintended 
transmitted messages from the midi keyboard?
Both Reaper and the midi keyboard are set to internal, neither is slaved 
to the other, since I don't need that right now.
Thanks,
Indi