How long have you had them and how how did you get them? I've kept PCF's for quite a while. Size is one way, they get around 2 inches max. The males will also start croacking once they get closer to maturity. My usual mentality is to simply drop off from every day with an occasional skipped day to every other day once they're near full size. Most frog species grow to their full size in about a year, give or take. The males will be a bit smaller than the females usually.