Need advice

I watch a 4 month old baby for her mom and dad to go to work. I’m close to the mom and dad but trying to keep some secrecy since I don’t know if anyone on here knows them.

She gets dropped off before 8 and picked up before 6 most days. When she gets here her diaper is so full of pee and a lot of the times poop that her clothes are soaked. She only leaves enough formula for 3 4 ounce bottles every day. I’ve asked for more and she made comments about not wanting her to be obese... I bought formula and keep it here and feed this baby as much as she wants! She’s dropped her off without any diapers for the day. Her parents are always talking about how bad of a baby she is and all she does is cry, but I’ve never had any issues with her being overly fussy. The baby has the flattest head I’ve ever seen. Her mom keeps asking me to fix it because they can’t do tummy time at her house she cries to much. She’s 4 months old and doesn’t even try to roll over when I lay her down. She cries so much when she gets picked up and if they’re holding her she watches me and follows me with her eyes and cries if I don’t hold her.

How do bring up these things without offending? I definitely don’t to make them mad and not bring her here. I need to know she’s fed. I’m so worried about this baby when she’s not here. I love her and her parents I just need them to do better for her...