My 5 month old baby is taking less formula milk after starting on solids?

I started introducing a bit of solid to my baby since he completes 4� months, he really likes it. Now he's five months and still taking one solid feed a day followed by formula milk (stopped breastfeeding as my milk has stopped coming out). But now for the last three days, he relishes on the solid food but takes only a bit of formula milk. He usually takes formula milk around 5-5 ounces every feed (5 times a day) but now he hardly takes in not more than 2-3 ounces. Is it because of the solid food intake?