Try adding 2.5 ml of a 10% solution of potassium bromide per liter to your developer. You can add more in 2.5 ml increments until fog is under control or until about 40 ml of bromide has been added. If there is still noticeable fog then the paper is beyond help.
You can also use 1% benzotriiazole in place of the potassium bromide.
hi Gerald!are there many differences between potassium bromide and benzotriazole???...a part the price...because the benzotriazole is very very expensive,while the poassium bromide is very cheap.