You have the same case as mine...But my BB was even worse than yours...
Since the days she was born, she drank so slowly..the first 3 months..i fed her almost an hour for not more than 4 oz... she cried everytime when she saw the milk bottle (she cried not very often )...when i told my friends.. they all suggested to change the brand..(I use the same brand as yours!!).. BUT my 99 said she used this brand to feed her children.. well this included my husband.. & she said this is good..so she sticked to this brand... i tried to change the milk powder.. but my 99 was the one who looks after my Baby... so until now my girl is now 20 months.. she has a good health - thx god for this BUT her size is SUPER SMALL... she doesn't like to drink milk much.. sometimes she cried when she saw the milk in the morning.. & we feed her bread for breakfast instead.. hahaha..if i had a choice again..i will change to other brand....
My girl also didn't like drinking milk before. It took her so long to finish her bottle. We changed a few brands but the situation didn't improve. End up, we have chosen Meiji. And we can see she has big progress. Now she can drinks 8oz within 20 mins.