Must be the tubulars! 
Seriously. This happened 2nd time. Is this the nature of Vittoria Triathlon tubulars? I most likely get flats during the race but the tire holds up to T2 and deflates later on. After examining both times there were small punchures on the tire that let the air out.
That particular tire is VERY thin, and is not, according to the BTR tests, not any faster than the regular CX. Try the Corsa CX, as that is a bit more of an all-around tire, which means it may be more appropriate for triathlons, where you don’t have a team car behind you to do a 5sec wheel change.
Yup, it is softer than my training clincher tubes!
What pressure are you racing them at? My race weight is 185 and have a hard time with flats if I pump my tires to 120psi. But never have had a flat if I use 100psi. Lower rolling resistance too (at the higher pressure the tire has the tendency to bounce ober small irregularities in the road surface instead of deflecting out of the way). Of course I have now cursed my self…
Get good tires, inspect them well, and replace before A races. I have done 145+ Tri’s including 16 IMs and have never flatted (in a race). I race on Conti Comp GPs and pump them anywhere from 140 - 160 PSI depending on the course.
OK, now I’ll Knock on wood :-)!
Slime Lite tubes. no flats in the two seasons Ive used them. Once in a while Ill see the green stuff on the tire indicating it saved me from flatting out.