Should I switch to a different type of milk preparation (Good Start for Alimentum)?

Based on the symptoms you described, it does not seem necessary to change to a different type of milk preparation like Alimentum. It is usually reserved for treating cow's milk protein intolerance/allergy. Since the symptoms previously disappeared with the drops recommended to you, it would be best to continue with those and try stopping them around 3-4 months of age when colic typically goes away. However, if any concerning symptoms like blood in stools, fever, projectile vomiting, etc. appear, please consult your doctor. I hope this helps, and have a good day!