From your description, it sounds like you’re using the MC6 Pro as a MIDI Clock master for the two other effects, and both of them are set to MIDI THRU (as they’re changing Programs).
You can go the CC route for Tap Tempo in the H90. But since MIDI Clock is sent across all MIDI Channels, it’s easier to sync everything to a single tempo source. Here are a few options to confirm:
https://cdn.eventideaudio.com/manuals/h90/1.9.7/content/tempo-menu.html
Next check the the H90 Programs used are in Tempo Sync. I’m not in front of my rig right now, but I would try using MIDI Clock Tap programmed to one of the MC6 Pro’s switches. If everything has been routed correctly, that should sync it all up.
