5.5 months old baby girl eats only 17oz of formula, help!!!

My 5.5 months old girl only take ave. 17oz each day. I normally feed her 5-6times 5ozs of formula. Her feeding was fine 2 weeks ago. I have just added oatmeal cereal & baby food to her feeding. The schedule is as shown below:

1am- 5oz formula
5am- 5oz formula(sometimes 2-3 oz)
8am- wake up
9am attempt to feed her 5oz formula, but she will only take 1-2oz
12:30noon- attempt to feed her 5oz formula, but she will only take 1-2oz
               - 2 teaspoons of oatmeal cereal & half container of Gerber's 1st food(veggie/fruit)
3:30pm- attempt to feed her formula, she only take 1oz formula
6:00pm- 2 teaspoons of oatmeal cereal & half container of Gerber's 1st food(veggie/fruit)
8:00pm- her regular bedtime. she will take 3 ozs.

She is teething and the bottom two already cut out and she keeps chewing with her back teeth for the last couple of days.
I find she is very hard to feed during day time but night time, she normally takes the whole bottle of milk with no problem.
Also, how much should i feed her in terms of baby food & cereal?
At her 4 months check-up, she was 14.8pounds(65percentile) & 25inches.(75percentile)

Please help & advice