What are your temps running, on average? For me, ~72F is ideal, and I use a small chiller to ensure that temps are stable. Also, it's best practice to thoroughly clean, sterilize, and rinse all your cloning gear between each run, pucks included. If you've had serious bacterial or mold problems, it may indeed be wise to replace all your pucks. It's a small expense for the peace of mind, in my opinion. :yes