A lot of times the spots on vinyl and pvc is a type of yeast and not mold, but the removal is the same. House hold bleach is typically around 6 % and depending how old it is can be very weak. I would recommend the outdoor bleach it is a little stronger usually at 9%. The best type to use is pool bleach, Walmart carries it and it is around 12% to 15%. A 50/50 mix with water should remove the spots. Mold Armor's primary stain removing ingredient is Sodium Hypochlorite (bleach) at less than 5%.
Another option is Corteclean it is a very highly concentrated Sodium Percarbonate when mixed with water it makes a very strong hydrogen peroxide. Using this may require a little scrubbing to agitate the solution.
Please make sure you use proper protective equipment with any concentrations this strong. Safety glasses, good kitchen type rubber gloves and old clothes as it will bleach most clothing. Good ventilation is a must.