Formula fed babies

How much milk is your baby taking? My sons intake has been so poor for probably around 6 weeks. His daily total is around 20oz and he used to drink 34oz when he was younger.

Today's schedule:

07.10 - 6oz milk

09.00 - porridge with pureed banana (70grams)

12.00- 5oz milk

13.30 - pureed Turnip (70grams)

16.20 - 5oz formula

19.10 - 4.5oz formula

He doesn't just drink 5oz at once its with encouraging and keep offering him it every 5-10 mins until bottle done.

I used to make 7oz feeds and now he would never take that.