My audio rack is bright, will sand fill help?

Filling the tubes with sand may not be a complete answer but it certainly can help.

I think you mean VTI audio rack. As far as I know, VPI doesn't make racks other than the one the TNT came on.

+1 for air dried maple shade rack

However.....

Instead of a whole new rack, go to the website and buy their super thick maple block beveled platform along with their heavy brass footers to synthesize the full rack effect.

I had the "full Monty" Samson rack from Mapleshade. Sure it worked but it was both excessively bulky and butt ugly, so I sold it.

Just to emphasize the alternatives, the NA approach is a heavy mass isolation approach, whereas the UK approach is a "light and airy" conduit isolation approach. Both work .... Which is better is entirely depending on your system.

I've had both.

With my current REGA Isis valve cdp and REGA Osiris amp, a UK approach custom made bespoke rack based on the Naim
Fraim. It performed significantly better than the Mapleshade inherited from a lesser prior kit, and the differences were not subtle. I can't explain why other than the dealer suggested that it is added synergy likely linked as much to the components sonic improvements as you move up the $$ ladder with your system and a better match for a UK designed rack with UK components.

FWIW....

I've never heard anyone say Lamms sounded "strident". Jesus, that rack must be awful. Try some softer footers from Herbies, maybe. But anything that makes Lamms sound bad should be thrown in the garbage. Really.

Symposium under everything on the rack will improve the sound very much.