Shedding or losing transplanted hair

[tj2014]

So I'm about a year and a half from my second hair transplant with no complaints about my results also been on fin for a while with no problems.

But very recently I've started to lose hair I believe only in the transplanted areas along the hairline and just behind has clearly thinned out.

There is no native hair in these areas so its only new hair that's gone and it all happened very quickly I had a haircut and it was all OK and as it grew back balding patches were appearing it took about two weeks.

So I'm just wandering what could be happening .