Hey Steve.
This seems to be fixed by simply opening up the decal materials (at least for me). Head to the /decals/Splashers/ folder and open up the material in question. The decals then suddenly ‘pop’ back to normal.
The main issue for me with forward rendering seems to lighting, or how the particles are being lit. The contrast is far too high compared to the normal deferred rendering - I’ll try and see what’s up!
James