According to this schematic it looks like there are 16 volts on the 25uF cap. It also shows that the 2uF is a 50V cap and the other two are 25V caps. The 50V rating is probably just something that was readily available since it shows the same voltage as the 2uF. Basically anything over 25 volts should work for all three of these. A lot of people will just use 25uF @ 50V caps because they don't cost any extra and it gives a little more safety margin.
http://schematicheaven.com/fenderamp...bass_schem.pdf