Going CRAZY!

I used to find it hard when there was only Mariah and J.C. to correct and discipline, now we are in over our heads! I have lost control over my children (two in particular) Mariah and Joshua, my biggest challenge! I think when we added Sierra and then Kaylee to the mix, my time became very limited and discipline no long fell at the top of the list. The phrase "pick your battles" always came to mind but now I'm regretting that deeply!
I'll start by a summary of the other children first! J.C. is not a problem child at all! She is usually very helpful! My biggest problem with her is attitude but perfectly normal as a teenager for that! I do, however, worry about her intense interest in boys!
Sierra is two and into EVERYTHING right now but as far as being defiant, she's not too bad. I do find her picking up the habits of the older ones and that bothers me a bit but I'm sure if I can stop their behavior, hers will too!
And Kaylee, well... she's 9 months, enough said!
Mariah was by far the best baby/toddler! she was never fussy and never went through the terrible twos! I guess I'm paying it for it now! She has become entirely too mouthy! She back talks at every chance she gets! If I ask her to do something she may not want to do, I get a fit and not just any fit, a fit like a two year old would through! She crys and stops and yells and says "everyone hates me! You hate me!" What really scares me is she's recently started getting violent about it. She will scream blood curdling screams and pull her hair. She will attack Josh and hit him, she's even bit him and that's NOT normal for an almost 11 year old. Today while her and Joshua were supposed to cleaning there room they were arguing and she said to him "How bout I knock your teeth down your throat." I was appalled and sad at the same time. What happened to my sweet little girl? I don't know where all the violence has come from. We do not spank her, Chad and I do not getting into physical arguments.... I have lost control with her.
Joshua is a name caller and he says No after everything! He usually says stupid to anyone and anything he is mad at. When I ask him to do something even the simplest things he immediately says "NO!" even if he's in the middle of doing it! It's so frustrating! He also wines a lot! Everything is a wine and he'll ask me the same question 10 times even if I'm on the phone or busy, if I don't answer right away he just keeps asking.
The two of them are ALWAYS tattling! UHG! OK so now what?
I've lost all control here and I need it back, fast! Anyone, please give me some advice! I NEED it! I know I need to be consistent but what else can I do? I am always quick to get angry and I HATE that! I feel like it just runs in my blood like a poison I can't get rid of! Lord, please help me to lovingly correct my children and regain their respect! Help me to have the strength to be consistent and wisdom to handle these situations.