Thank you Pentaxuser for your input, much appreciated! My processor is a basic Nova Monochrome model, with a red cover, which is not really air tide at all. Perhaps that is why my Ilford MG is loosing its power after one week? I love an idea of using Nova processor in my tiny darkroom, but I need to get a better paper developer or new Nova processor with a proper cover. I was thinking of getting a new processor from Nova, but the cost of the unit itself and the shipment to Canada is rather very high... so, searching eBay for a used one
But for now, I will try different developer (Ansco 130).