Felku, I'll chime in with the vast wisdom of a total of two blues made, one of which is still aging ...
7 days to seeing blue does not seem excessive to me, but 1/4 tsp of PR does! I don't think you need to use that much, and it is relatively expensive, so you may want to cut back ... for the 4 gallon Gorgonzola recipe that I made recently, I only used 1/32 tsp. Of course, that was in just 2 gallons of the make, but still -- plenty of blue showed up.
Hopefully others with greater experience will offer corrections or other input!