A charcoal filter WILL help remove some things, including chlorine from the water. They do vary in effectiveness over the life of the filter. It depends on the amount of chemicals in the water and the amount of water you run through the filter.(posted 8632 days ago)Charcoal will not cause any trouble with your chemistry. Every charcoal filter has a final particulate filter to keep the charcoal from getting out.
What I did (very hard well water) was to buy a table top distiller (Sears in the US). This distills 1 gallon of water in about 6 hours. I have a 10 gallon storage tank and use distilled water for everything except washing. Tests have shown that distilled or very soft (low mineral content) water increases wash times tremendously.
However, I agree with John that as a test you should process with distilled water thoughout the process and see what happens. If things go back to normal, try distilled water for everything except the wash. If this is fine, you can either test more or use distilled water for all chemical steps. If you continue testing, the developer step is most likely to be the one sensitive to water quality.