Competition finals are happening in the US! To really clean your saddle pad and get it too look whiter, stain remover is always my go to, but I also like baking soda. It also helps remove any smells. The same is with vinegar. If the stain is too strong for that, then I recommend a whitening spray (could be one for the horse or just spray paint). The downside to that is it can look a little crusty, but if you use a toothbrush to help get it into the fabric, that should help.