Why are my brake calipers leaking?

I have 65 Mustang with a Stainless Steel Disc Brakes conversion on the front. It's the stock style system with the four-piston calipers, nothing fancy. I just had them rebuild my passenger caliper under warranty due to fluid leaking out around the pistons all over my pads and rotor. They were even nice enough to replace my pads even though they aren't warranted.

Now I think I'm having the same problem with my driver side caliper. When I blead the caliper off to put in my new pads I noticed that fluid was oozing out around the dust boots on the pistons. Isn't there a seal behind the dust boot that should be containing the fluid? I wouldn't think that there should be fluid directly under the dust boots. Anybody else have experience with this?

Thanks

I called their tech support about it this morning. They said there can be a small amount behind the dust boot, but it should be no than a thin film. He said if it's enough that fluid is leaking out then the caliper probably needs rebuilt. It just seems odd that both calipers go out at the same time. Last night I tried to burp as much fluid out of the boots as I could and then sprayed everything down with brake cleaner. I'll check it today and if it's still leaking then I'll send it in for a rebuild. This isn't one of those things that I want to road test to be sure it's working.