FF baby suddenly drinking less

[VickstaS]

My 17 week old FF baby has seemingly gone on milk - strike. He was previously drinking around 1.1-1.2 L a day over 6 feeds. Almost overnight he refused to drink more than 100 ml per feed whereas previously he was draining his bottles. He also was sleeping from 7.30 to 7 am at least 5 nights a week, now he is waking for additional feeds ( unsurprisingly, as his consumption has halved!). He is a big chap (91 st percentile) and has always put on weight as expected. He has been drinking the lower amount of milk for about 3 days now.
He grizzles at similar times to normal to signal he is hungry, drinks the first half of the feed normally, stops for a burp, sometimes has a small sick, which is normal, but then point blank refuses to drink anymore, and cries is I persist to try and get him to drink.

Any ideas what this is about? Do babies have the opposite of a growth spurt? Could it be teething? I certainly can't see any teeth but I can imagine he may have sore gums if they are moving around in there. Just a phase?

We tried him with a cup but he wasn't that keen on that
either.

I guess I could try teething granules or calpol on case he is in pain? Otherwise just wait and see if it just a phase? I won't see my health visitor until January but will ask her about it if it is still an issue then.

It's just that it's not like him, he is normally very keen on his milk, so am a little concerned.

He is my first so probably over-worrying!

I'm no expert as DD is only 15 weeks old, but here are a few ideas:

DD often only drinks 100ml when first offered a feed and then wants the rest half an hour later (or sometimes 5 min later or 1.5 hours later), though she has pretty much always done this. She will sometimes refuse any more as if she is full then 5 min later guzzle it as if I have been starving her.

Could he be ready for the next teat up?

Does he get distracted? DD will stop and want to do something else for a bit.

Is he showing other signs of teething?

Could you phone your health visitor service? I did this last week and it put my mind at rest and turned out to be a really good way to get information.

He could be ready to be weaned. DS2 did this at about 6 months, and DS1 at about 4 months. Just got bored of milk and wolfed down food.

It sounds perfectly normal to me. They just go through phases of more or less - it's fine if he's otherwise healthy. Or he could be starting with a cold or something.

Current advice is to not start to introduce solids before 6 months, especially if there's any family history of allergy.