What helped us was actually trying cold milk instead of the usual warm bottle, because apparently the cool temperature can soothe sore gums while they drink, so it becomes less uncomfortable for them. At 11 months, babies are also naturally starting to rely more on solids, so if she's eating well, her body may genuinely be shifting its needs a little, but 300ml does sound quite low, so it's worth keeping an eye on it. That said, since this has been going on for two months, it really is worth bringing it up with her PD or a child health nurse just to rule anything out and get proper guidance for her specifically, you're doing a great job by paying such close attention. Hope it gets easier soon!