I would redo the silicone around the tub by heating it with a hair dryer, using a plastic tool once it’s gooey. https://youtu.be/_DI4hfHM_Hg?si=9ZmediVIP1IZ24_7
In between the tiles you can try grandmas stain remover and a firm toothbrush https://image.nostr.build/5e150b6b85fdeb0a1c6ea896c2cda399bd419b866bdc76068ba415fec5f093ce.jpg https://image.nostr.build/866b00a987045d794b54bb96799724bc48a722ac7a8cd2ab22bb193bce73e748.jpg https://image.nostr.build/afd2026cbe627260d329a31c7fbf02167a5ba842b09511c1940c3edbd5108b0d.jpg  

 Try bleach yet? Just spray it and come back in an hour. I also like 3M heavy duty brushes you can put some elbow grease behind. 

Where the tub meets the tile use a bathroom caulk. Run a piece of painters tape, run a bead, dip finger in windex or use a silicone glove to run your finger across the joint. Pull the tape. 

 https://hips.hearstapps.com/vader-prod.s3.amazonaws.com/1678736977-granite-gold-640f7e4c912b0.jpg?crop=1xw:1xh;center,top&resize=980:*

Power drill with a brush attachment works well too. 

 believe it or not, toilet bowl cleaner. clears out serious stains.