This article has some more details about TD's time in the military:
A man in central Washington state is wanted on suspicion of murder after his three young daughters were reported missing and then found dead.
www.military.com
Specifically -
"Decker joined the Army in 2013 and transferred to the Washington National Guard in 2021, Washington Military Department spokesperson Karina Shagren told The Associated Press. He was a full-time member of the Guard until 2023 or 2024, when he switched to part-time.
Decker stopped attending mandatory monthly drills a little over a year ago, and the Guard was in the process of a disciplinary discharge for him, Shagren said"
and from this article:
‘He keeps getting more unstable’: Wenatchee mother raised alarms before daughters found dead
"On Nov. 14, 2022, a petition of divorce was filed in Chelan County court by Whitney. Within the document, she noted that no protection order or restraining order was needed."
... more timeline entries in the article snipped for clarity ...
On Mar. 7, 2023, a parenting plan was finalized, again noting no concerns. Travis was scheduled to have the girls every other weekend, from Friday at 6pm to Sunday at 6pm.
A year later, according to the court documents, Whitney’s opinion on the mental health of her ex-husband appear to have changed."
So it sounds like whatever changed in his psyche happened relatively recently.