Really worried about my DGS

[PurpleOne]

Hiya all> my first post in the preemie section as I have a few concerns regarding my DGS and my DD1

My dd1 is 17 yrs old and my dgs is nearly 10 weeks old. His edd is 25th May and was born 22nd March. He did really well in NICU and the SCBU and he came home nearly 3 weeks ago.
A beautiful contented little boy and I love him to bits.

However, my dd1s partner tried feeding him gravy last week. To which I had words with both of them. Later at the weekend, they came to visit and do washing etc (they live in a hostel) so I made dinner for them. He openly shovelled mashed potato into DGS mouth. He could have choked, not to mention the salt content and cows milk.
I visited the hostel last week and DSG is having Nutriprem every couple of hrs. I did not notice a kettle in their room and certainly no kettles in the communal kitchen.

Anyway, I messaged his partners mum and dad mentioning this fact about the potatoes and gravy as this has happened twice now and maybe they could get the word across how dangerous this is. I also expressed how many times DSG was being thrown in the air (and caught) but cannot hold his head up yet.

The final straw has come today when I saw dd1's facebook pictures where they went for an innocent trip to the park. On looking more at the pics, they took a 10 week prem baby up a very high slide and in one picture, DSG is laying face down in her partners lap while sitting right on top of the slide.

I have talked myself dry to them and they continue to do their own thing whilst, I feel, putting him at risk.
I have a darling first born DSG and he is absolutely gorgeous. Such a beautiful baby and so content.
I know I did the right thing in messaging his parents cos they weren't listening to me, they have now cancelled my first every babysitting stint. Was hoping to give him a bath as he really smells and has milk in his hair.
I do not know who or where the HV is.
Would any of you actually be calling the SS about this? I'd never forgive myself if anything happened to him and I sat back and did nothing.

WWYD?

Thanks for listening
I have got it right in the neck for being an interfering old cow and her partner is refusing to visit.

If his due date was 25th May, then he is still technically at the new born baby stage rather than 10 weeks. Although his birth date was in March for most areas of his development his age will be corrected for the number of weeks premature.
On discharge on hospital, premature babies are often monitored by a community nurse from the hospital who weighs the baby. So you could check with the hospital to see if this was the case. Once they are satisfied with his weight gain his care would be transferred to a health visitor based either at the GPs practice or local health centre. However they may not carry out home-visits. They may expect dd to visit a baby clinic.
Are there specialist groups in your area for teenage mums? The HV may be able to recommend one locally which is able to provide support for your dd.

I went to the childrens centre and got the number for SS and the local SCBU where he was discharged.
Phone calls have been made now - I hope that they get the support they so obviously need.
Thanks for your reply. I also posted in chat.