Re: need feral cat help
Welcome to Cat Forum. I've never managed a colony, but I have trapped the kittens to tame/socialize for adoption and TNR'd the adults, all of whom were slowly tamed/socialized outside and then transitioned to becoming our housepets.
When Malibu's litter was about 4wks old, she moved them off our property. She brought them back about 4wks later, on field-trip sort of visits ... and I was able to trap them in my garage. When several weeks of work wasn't producing any results (none would approach me) I separated them and brought the litter into my bathroom to tame/socialize and Mallie was spayed and released. In less than 5mo she allowed me to begin socializing her and she has now been my bestest-buddy for several years.
I *think* at this age, the Mamma-cats begin to take their litters on 'field-trips' to learn their territory and how to survive in it. I also suspect that some kittens, who don't pay attention and keep together, may get left behind and lost. If they were older (around 5-9mo old) I would suspect them of 'wanderlust' and wishing to search out and establish their own territory, but being young-ish ... I'm leaning towards field-trip, possibly field-trip-gone-awry.
Best of luck, I hope they all return.