I would have a huge issue with this, OP. I don't understand the relaxed attitudes to alcohol intake at all. I think people are too quick to forget that alcohol is effectively a drug (the last legal one at that) and it is highly addictive for many. It can become a problem very, very quickly. It's all very well for folk to say, 'Leave the poor man alone. It's only a couple of glasses a night.' But what happens when two glasses morphs into two bottles a night and he's too pissed to make it up the stairs? Is the OP allowed to intervene then, when it's already become a problem?
Watching the man you love go from being an active, healthy non-drinker to somebody who is less active, gaining weight, a lot quieter and drinking frequently is a relevant concern, imo. I'd be wanting to know why he felt the need to drink so frequently and if anything was bothering or upsetting him. Yes, people change. In a multitude of ways. Sometimes we put on weight, sometimes we start smoking or drinking, sometimes we lose interest in things. But there's usually a reason why. I put on a fair amount of weight during my pregnancy and have added to the flubber gradually over the years. I've done so because I've been unhappy about various things and I comfort eat. It's unhealthy and I need to stop. I recognise this and I'm trying to adjust bad habits. It could be that the OP's DH is comfort drinking. But she's not going to understand the problem (if there is one) by staying silent.
If the OP had written that her DH had started smoking, I bet there would be a chorus of, 'Disgusting habit!' and 'So unhealthy! He's setting his kids a bad example!' and 'Beaurgh! The smell! I bet he stinks!'
Yet drinking frequently is okay? Alcohol can turn the most civilized person into a complete train wreck. It makes you smell, it makes you annoying, it makes you bad company the following day and allowing your children to grow up around frequent binges sets a bad example.
Now I enjoy the odd tipple as much as the next person. I love nothing more than taking a bottle of wine to a friends house for a catch up or going out to the pub every now and then with a group of workmates. It doesn't happen very often, but I always look forward to it. It's a social thing. But for me, the line is more than crossed when somebody is buying and/or consuming alcohol on a nightly/several times a week basis. That for me would be a red flag and no, I wouldn't be happy about it. At all.
So no, I don't think YABU to object OP. People's attitudes towards drinking vary greatly though, as you've seen on this thread so far. I think all you can do is broach the subject with him again, preferably when he hasn't had a drink, and let him know that the sudden change is bothering you, that you don't like the frequent drinking and you want to know if anything is troubling him.
for you. I hope you can get it resolved somehow.