Discover and resolve excess PHP5 instances using memory

I've not changed anything on my server but in the last 3 days the memory use has gone from 250Mb max to 1Gb. My current top: Tasks: 394 total, 1 running, 393 sleeping, 0 stopped, 0 zombie Cpu(s): 20.8%us, 1.7%sy, 0.0%ni, 76.8%id, 0.0%wa, 0.1%hi, 0.7%si, 0.0%st Mem: 1254400k total, 1006984k used, 247416k free, 0k buffers Swap: 0k total, 0k used, 0k free, 19528k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 19843 root 20 0 147m 42m 20m S 0 3.4 4:48.27 apache2-ps18939 24671 insider 20 0 86220 27m 5852 S 0 2.2 0:02.65 [login to view URL] 30424 dhapache 20 0 147m 24m 1800 S 0 2.0 0:00.02 apache2-ps18939 30191 dhapache 20 0 147m 23m 1768 S 0 2.0 0:00.04 apache2-ps18939 30477 dhapache 20 0 147m 23m 1704 S 0 1.9 0:00.00 apache2-ps18939 30971 dhapache 20 0 147m 23m 1704 S 0 1.9 0:00.00 apache2-ps18939 29844 dhapache 20 0 147m 22m 788 S 0 1.9 0:00.00 apache2-ps18939 29832 dhapache 20 0 134m 22m 568 S 0 1.8 0:00.00 apache2-ps18939 26499 insider 20 0 76776 20m 5960 S 0 1.7 0:04.08 [login to view URL]