When working with bigger processors like my Colenta 66, ageing of chemistry always is an issue. More so as its tanks take 11l of each chemistry.
The easiest remedy for this is running the processor a lot. Each m2 of developed print adds a few squirts of fresh chemistry to the tanks, while exhausted chemistry is removed. So the more throughput you have, the better your chemistry is.
Or you switch to a processor like the The Termaphot ACP 252. I use it during times when I don't want the pressure of working in the lab daily. It does only develop paper up to a width of 25 cm (the Colenta does 66 cm!), but it does so with only 2 liters in each tank! Even if the chemistry goes bad not much has been wasted.