If the dots are coming from edges where the walls meet the bath, then the caulking has degraded needs to come out. Bleach will not do the trick as the caulk used has become stained. And even if it did appear to remove it, the mold is really not gone, only bleached white where it blends into the materials around it.
If there is no caulk and simply a edge where it appears that the mold is coming out from, you have a bigger issue. The mold can be coming from behind the plastic liner.
Understand this. Mold needs food, air and moisture to live and survive. You cannot do anything about moisture, and air in your case its a tub. Mold will not grow on the plastic as it is not organic. So it is growing on something else. It can caulk, built up soap that has not been thoroughly cleaned away, or coming from behind the wall where perhaps wall board is located.
In the case of plastic tub and liners, you are not supposed to use a rough scrubbing tool such as scrubbing pads to remove difficult soap build ups. This abrasive nature puts scratches in the surface where more soap can get a better adhesion making it harder next time to remove. Its in these tiny scratches where soap is still present allowing the development of mold to still exist.
So your fix is to determine what the mold is growing on, and in your case I suspect soap build ups. And use a cleaner that will remove the built up soap scum. Once removed, if it is in the corners, remove the caulk and re-apply a good quality sealant designed to be used in shower and tub areas that has a micro-ban in the mix.
I have a tiled underground wet room, I hate housework so when the grouting starts looking mouldy and grey, I spray with Dettol mould and mildew. That's it! It just bleaches away the mould, it even fades mould stains on rubber. Try it, it is a bright green spray bottle. Watch out for mats as it bleaches anything it drips on.