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