Isit normal for supply to drop after 1 day of engorgement and fever?

Hi this is definitely normal. Has your fever subsided by the way? It could be mastitis and you may need to see a doc for antibiotics if the fever persists. It could be you have a blocked duct which was not cleared that's why it is engorged and causing the fever. You will have to clear any block duct by massaging especially the sides near to armpit is where blockage always occur. Feel for hard lumps and press it out. Hand express after latching or pumping to express out all the milk will be good to clear any blocked ducts. You can also get a massage lady or see a lactation consultant to help clear the blocked ducts. Once blocked and having infection or fever the milk supply will surely drop.