That's very short, bit is it that diafine just goes to completion then stops?
3+3 means 3 minutes in bath A + 3 minutes in bath B. I use a normal agitation ( 2 inversions per minute) while the film soaks in bath A and almost a stand development with bath B. No trouble so far with Tri-X @ 1000 ASA.
"The problem with photography is that it only deals with appearances." Duane Michals
"A photograph is a secret of a secret. The more it tells you the less you know." Diane Arbus