They may swell slightly more, which will add a bit more weight, but not normally too much after week 5/6.
Depends on the plant, I have had a few just keep fattening till they're done.
Mostly maturing to come.
It's like you have an orange tree full of green oranges, it won't grow many more, but the ones that are there will swell and go from tasting terrible and bitter to being sweet and juicy.
Plant mass is not half as important as resin mass, often tiny high quality flower has more resin than huge fat colas, so size isn't that important IMO... unless you're selling, then G's = $, but better G's = better $ :P