Clean bathroom shower grout
Paint with chalk paint & seal.
I've heard bar keepers might work I'd research that. Hope it helps
Make a paste of baking soda and water then apply it to the grout. Let it sit for a while - even overnight then rinse well. I hope that helps. Wishing you the best.
Hello! Heres some other recommended cleaners
The Best Way to Clean Grout-EVER!!! | Hometalk
Painted Tile Grout Refresh with grout pen
Grout cleaning/ grout removal and replace it
Here’s a Hometalk link for you to consider. Hope this helps
Sound like you need o dig it out and put new and put a silicone sealer over it after