6 week old

Every evening/night my daughter gets a bottle at 8 pm then sleeps till 11 pm and wakes up for another bottle. For about a week or so only at the 11pm bottle shes been sooo fussy and seems like it could be gas. Thats the only time shes fussy and its for about an hour and a half then finally falls asleep and is good for the rest of the night. Why could this be happening? Drs said try gas drops but I really dont want to give them to her every bottle if she doesnt need them then. If I just give them to her at her 8pm bottle will that work? Also does this resolve on its own?? Help this momma out! TIA!!!