How do you care for your below the lens filters? My sets have lasted for many years, but the no. 2 and 3 are showing their age.
I have a Kodak set and an Ilford set. After I am done enlarging for the day, I replace the filters in their respective slots in a covered box, but I notice that my most often used filters have developed splotchy little spots. Also a bit of dust.
I have washed with soap and water, successfully, I think. But some spotting is persistent. I can't advise using PEC-12 photographic emulsion cleaner, as it will made a swirl of my No. 2.
I did just purchase a new full set of Ilford filters, to be cut and replaced in the below the lens plastic filter holder. Really though, I only need to replace the No. 2 and No. 3, my most often used filters. In about thirty more years I am going to have a lot of extra no. 0, 1, 4, and 5 filters, I guess.