Senior Bichon Passing Small Stones and Blood Clots
Passing gritty stones and blood clots isn't normal and needs a vet visit soon. Clots can come from bladder irritation by stones, but they can also come from infection or a bladder tumor, which becomes more common in older dogs. Small stones can also lodge in the urethra.
Go right away if she strains with little or no urine. Ask your vet for a urine culture, imaging, and analysis of the stones she passes; repeated struvite stones usually mean a recurring infection that needs to be found and treated.
This is general information, not a diagnosis. Please follow your own vet's advice.