Grounding teens helpppp!

My step kids (12 and 13) live with us full time. They’re typically amazing kids and we have no issues with them. However the more time they go to their moms, the worse their behavior gets. One of the reasons we have custody lol. They’ve been there quite often lately since there’s no school now. We’ve had issues with them telling white lies pretty often the last 2 months, it used to be a BIG issue at their moms and we sorted it and haven’t had a problem until lately. This last weekend they were at their moms it was a big lie and very, very sneaky how they went about it. We quickly caught it and had long talks and took their phones and video games away. They’ve also since being at their moms more been really disrespectful towards us. They have a SUPER easy life here compared to there. Own rooms, TVs, phones, we never yell, peaceful home, live right on the lake, next door to their cousins and grandparents, they only have to do 1 chore a day, very loving. At their moms our daughter shares a room with 2 younger sisters, constant drama, she yells and curses at them, makes them clean the whole house every weekend, doesn’t cook ever, they have to feed themselves. Reason we got custody was the kids chose to live here because she was getting so crazy. Now I’m thinking it’s because we have more and provide more. We don’t spoil them, they earn their things. But we are better off and can give more. Over there they get hardly anything, but when they do they act like she’s the best parent ever and brag. She got her stimulus check and gave them each $100 and took them shopping...which we are very against outings right now. I’m just exhausted. I’m 34 weeks pregnant and hormonal. I’m upset. After grounding them and talking to them, the next day they didn’t even do their 1 chore. We don’t remind them bc it’s been the same chore for a year now. Never said sorry still, day 4 now. Idk if we ignore it and move on, or what. It just seems like it’ll get worse as it has already.