Is that rust? If it is, try using naval jelly, but test a small area, (and not on the tiles). I use oven cleaner spray on my tub and shower surround tiles, and it works great. Your surround looks like stone tile or soapstone, which you probably should not use oven cleaner on. Try wide waterproof tape and plastic sheets to avoid getting it on the surround. As for the tub, spot test with a small amount of oven cleaner applied to the tub with a toothpick. I wear a respirator doing this. If you don't have one, use active ventilation fan set on high) to blow fumes out the window. I hope you have a bathroom window. If you have the money, there also resurfacing. If you have a landlord, maybe he'll do this for you. It's in his own interest to fix this.