6 month old refuses bottle...

Brittney
My son is now 6 months old! About a week ago he started to slow down on eating... normal feeding schedule 
is 6 ounce bottle at 6:30-7 am 
4 ounce bottle with either cereal or stage 2 baby food at 11:30-12:30 
6-7 ounce bottle between 4-5 pm 
And his last bottle is a 7 ounce at 9:30pm. 
Now He barley eats! All he does is chew on the nipple and refuses both formula and solids. 😐 any advice?