Please let me know

KJ
We started solids with 5 mo old baby boy last sunday. He loved the solids but now it is a huge battle to give his milk. I gave expressed bm from week 6 via bottle. He usually had 700-800mls per 24hrs. Now he has 540-600 max with a huge struggle. Is this normal?? I have lot of frozen breast milk in the freezer. I am so anxious now whether he will refuse it. 😩