Great starting became hard starting.

I have a rebuilt la 360 with about 500 miles on it.
262 comp cam
holley 600 with electric choke
hei ignition
18 degree advance ignition timing with 35 total.

Its not really a problem but not sure what happened. Car use to start excellent when cold. Touch the key fire right up, no need to touch throttle. Warm up on fast idle, blip the throttle, idle nice. Did not change anything but a few day ago came out to start and had to crank for 4 or 5 seconds. When it did start it ran rough and wanted throttle to keep it running. When it warms up it runs and idles fine. So I am wondering what changed? I checked the timing and fuel level and both are fine. I checked for vacuum leaks and changed the PVC with no change. I checked that choke was closed and it does if you tap the throttle, when closed. Choke opens when running. Any ideas what to check next?