Bleach breaks down organic materials! A tail can literally disintegrate if used to often or in too high a concentration. There are much better products on the market! The bleach only helps with staining, not the normal yellow tint of a white tail- which bluing shampoos CAN help.
ALL white tails will yellow, it's their natural color. The cells of a white tail are are "clear" and since hair over a few inches is actually dead, the dead cells when they show light through them have a yellowish tinge.
The good bluing shampoos work because the bluing is actually a kind of dye that counteracts the yellow (doesn't remove the yellow, but tints it bluish, which the human eye sees as white) I always use bluing shampoo on my grey and white horses. In between baths I try to use a bluing spray, which helps with day to day control of yellowing tails.
Unfortunately there's no bluing spray on the market but I recommend 1 teaspoon Mrs Stewart's Bluing added to a bottle of Infusium 23 leave in conditioner. This conditions manes and tails while gently whitening.