I (F21) think my LDR boyfriend (M24) is getting bullied/harassed at work, he won't speak up and it's affecting us, what can I do?

Been together for 2 years, long distance (I'm from the UK and he's from South Africa - hes recently working/living in the United States). He started his work there in October and already moved onto leadership/management position in late January. This one girl (Call her Daisy, F24) got there in January, so was there for some of his leadership training and ig there was that awkward transition of colleague -> boss between them?

A bit of a unique circumstance to this job is that you live and work with these colleagues (Small bubble, about 3-4 workers staff members per site), so with the wrong people you can easily clash and get on top of each other. Daisy is super gossip stereotype and snarky, I met her on one of my visits and didn't like her much but tolerated.

Now they've gone to another state to help at a different site and he doesn't work his managing role there (the guy who trained him does). But another girl (F26 - Annie) has rocked up and she's even worse than Daisy and they got on very well. Only been there a few days and making snarky comments, interrupting our phone calls during his off time (he goes to a private place, but they walk over..ie: legit opened the car doors on opposite sides and stand outside, talking through) and they will laugh about anything I say over the phone. It's become really uncomfortable now and every day since he's been in a very low mood, i cant do anything about it cus im not there. This is the handful of stuff I've been able to hear myself or the few things he will tell me. One example was Annie made a comment about his legs being too weak to carry a bucket of water (in front of the others). Idk if she's just insecure because he's a very fit guy etc, but it was so out of context and someone had her apologise on the spot, but asides from that, no one calls her out on her bs.

The two girls are both leaving the company in 3 weeks, so my bfs mentality this whole time is to just get through it and not cause drama. But this long distance stint is already tough on us currently due to other circumstances and this whole thing is clearly draining him and myself really, putting us both in low moods. Not to mention, if they were to ask for references at this company, they'd get great ones without any record of their behaviour as colleagues.

I honestly think he might be embarrassed to report it cus he's a guy reporting 2 girls being rude every day and I can get that if you take it simply, might feel a bit crap to report that. But it's getting exhausting and anyone would think they're high-school girls with nothing better to do with their lives. Any advice?

(Sorry this was a hard thing to try sum up)