Are you breastfeeding or bottle feeding formula? If you are breastfeeding as in directly latching, baby can get distracted by lots of stuff going on now that they are older and wants to participate more in their surroundings. So they tend to drink lesser milk in the day and made up for it by waking up at night for feeds. If you are bottle feeding formula milk, check whether she's drinking lesser now. Or maybe she has a bigger tummy now and wants to drink more. Try to delay solids to 6 months old though coz babies' tummy will be more mature for solids.