What happened?

Using Sildurs Vibrant Shaders, the redstone particles and water bubbles and droplets are visible through shulkers, chests and signs (not a complete list, these are the ones I have encountered).

Screenshots

Iris and Minecraft Version

iris-mc1.16.5-1.1.0

Are you running Sodium along with Iris?

Yes

Operating System

macOS 10.13.6 (High Sierra)

What is your GPU?

GTX1080

Java Version

Java 13.0.2

This does not appear to be an issue in Iris 1.1.2 on either 1.16.5 or 1.17.1 with Sildur's Vibrant Shaders. Maybe it was fixed in the meantime.