That was how we ended up with now SS14.  I know you already have primary, but a good therapist can help the kids to deal with the trauma of being with BM and/or help get her visitation reduced or removed. 

Send the Skids back with granola bars, etc.... Sadly, you have to tell them not to tell BM or anyone else in teh home and to eat in private.

Hopefully BM ends up in prison for a very long time.

Start calling CPS directly when teh Skids arrive stanky and unfed.  Overload the local CPS with calls and complaints and kick the Judge in the ass using CPS.

Never stop.  Nail BM with every posible complaint, child neglect, endangerment, etc, etc, etc...

That said, we understand how you feel. We would send SS-31 to SpermLand visitation a clean, happy, conversant, and mostly toilet trained toddler/little boy and we would get back a nasty dirty waif, not talking, and with a case of BM that would make a septic worker proud.  He would have black sludge under his arms, in the crooks of his elbows and knees, around his waist, puss filled welts on his butt cheeks, diaper rash so bad  and raw his anus would bleed when we cleaned him.  We started taking him to the doc just before going on the airplane then on the way from the airport home to get an official record of his pre and post visitation condition.  

SpermLand courts did not give a shit.  The idiots in the Harry Potter robes slinging the Fisher-Price wooden toddler hammers ignored the facts and spouted "Any child would be blessed to have the love and care of his wonderful family" bullshit.

My DW even filed a CPS complaint against her own parents. Their home looked like an episode of Hoarders.  They left SIL then 15 alone for months on end with no food, in a rodent infested hoarder haven.  CPS told DW that SIL was old enough to work and buy food and to clean the house.

You can't fix shit people. Whether they are shit parents like your Skids BM, a shit family like my Skids SpermClan, or shit people that work for CPS and the courts that are supposed to protect kids.

The kids need to be in therapy so they can learn the skills they need to deal with their mother. The 12 year old needs to learn how to stand up for herself as well as how to take care of her own physcial needs - a therapist can help with that. The other advantage is that if they tell a therapist about how they are being treated at BM's, the therapist may report her for child abuse.

Not feeding kids is not taking care of their basic needs and that is neglect 

Probably depends on the area; some CPS systems are overzealous and ready to snatch kids from their parent for no valid reason while others look past abuse (or worse) 

An attorney should be consulted with considering the step daughters admissions of their neglect while at their mothers house so you will know how to legally proceed

Venting feels good, But in this case you need to do something.  Buy SD a cell phone. Even if it's a Walmart pay as you go pre paid cell phone. That will give you texting. And calls. Some internet.   Check in SD when she at BM.  If BM is locked in her room not doing anything pick her up.   I would call CPS. But they are so busy that this isn't high on there list, but good for court. You are trying..  plus this kid needs mental help, she needs to see someone 

Teach SD to text you when she's  in need  and consider a well check visit by the police.  If the court won't give her consequences, then you need to figure some out that you can make happen.   Think outside of the box and ask your lawyer for some.  

I would keep the pressure on regarding dragging her to court for the arrears.  Sometimes when you bare their asses firmly and frequently enough... these types just go away.  Sad for the kids. But often best for the kids and the quality side of their blended family life.

It may even be best for the toxic opposition.  Reduces their stress.  Though I would never forgive their arrears. I would keep banging on them for payment for as long as it takes for them to pay using CSE and the courts.

The SpermClan paid though the Spermidiot never paid a cent. His mommy, SpermGrandHag, paid his CS on all 4 of his spawn by three different baby mamas.  She raised the youngest three in her without a cent from her idiot statutory rapist son.

We never denied visitation, but we never agreed to additional time either. Not until his final COd visitation the summer before he turned 18yo.  SS asked if he could stay an extra ten days and be there for his 18th birthday. He had never been in SpermLand for his birthday.  They always took their visitation early in the summer to deny my DW the July 4th holiday.  They would then try to get extra time for various reasons. Nope, play stupid games, get stupid results.  

His mom and I discussed it and agreed he could stay.  That injected risk that he might not come home after his 18th Bday.  We put a mitigation plan in place. We flew my BIL2 out to visit and so DW and BIL2 could take a brother and sister road trip from TX to SpermLand so DW could be there to collect SS the day after his Bday.  If he was going to choose to throw in with the SpermClan we wanted him to have to tell his mom f2f. 

I flew out and we did a three of us road trip back home.   SS -31 was very quet and brooding the first day or two.  He started opening up when we got to the N Rim of the GC.  All it tookw as a "WOW!" and the flood gates opened.  First, he called us out that he knew why his mom had road triped to SpermLand to pick him up.  He also informed us that he knew where his home was and who his real family is. We had a great late summer vacation. Several Nat parks, etc... (Crater Lake, N. Rim of the GC, Big Bend, Monument Valley, etc....).

We never tolerated any crap and we made sure that they followed the CO.  We also made sure that SS knew the facts including the CO, etc... In an age appropriate manner.

Do what you know to be best for your family including your Skid.  If the kid is not wanting to fully engage on travel ball, then BM can foot the bill and schlep the kid to practices and tournaments.  After all, DH pays for his share of all fo that with his CS.