DS2 has been referred to SALT.
He's 19 months and entirely without verbal language, but he is not ASD, I believe that whole heartedly. His communication is excellent, he is happy and interested in everything, always on the go, loves people, loves animals - polar opposite of DS1 who does have ASD. But DS1's first "thing" was speech delay, so I am mildly freaking out.
Hopefully the HV is just being careful because of DS1's history, but it does feel like a kick to the head when I was there about DS1, and she was more interested in DS2's behaviour.