If this is the case, it does not mean that the entire quantity is unusable because very small amounts of oxidized species can produce an intense coloration. My suggestion would be to mix small batches of process solutions using the dated chemicals to test their activity. If not, then it might be more prudent to discard the chemicals. Can be used straight or diluted to match tone. These products are applied with a fine brush to the toned print.
Distilled water is recommended for dilution.
I've used them after hot-press mounting the print on archival mat board. A more recent product is Spotpen, a series of 10 nylon-tipped pens varying from black to light gray. Enclosed are two examples of problems I've encountered with these products. This is generally not seen directly, but is noticeable when the print is slightly tilted and viewed from an angle in reflected light. This resulted from using a very dilute dye to slowly build tonal density to match a delicate sky print value.