Mold in tub caulking
I have used vinegar many times to kill mold. Spray it on the area where mold appears and let is sit for 15 minutes, then rinse off. Bleach kills surface mold but doesn't penetrate below the surface to kill the &quot;root&quot;.
You'll want to remove all the old caulking and then clean the area. Fortunately, vinegar works to remove old caulk, so does alcohol. After the area has completely dried, get a quality silicone caulk and apply it to the seam. let it fully cure, about 24 hours.