do you have star san and a spray bottle? that should help to identify most leaks. check EVERYWHERE. it's obvious you have a leak that you previously didn't see, and since you didn't check everything, it is highly probable that an area you didn't check is where it is leaking.
if the star san in a spray bottle doesn't help you, and sometimes it won't if the leak is really slow (personal experience), then you have to go to the water dunk test. dunk everything you can into a tub of water, and watch for bubbles. be very careful when doing this with the regulator section, as you don't really want liquid in that area. i had to do this with some of my regulator equipment, but i was very careful.