We had that problem with Bitsy too. She's much better at it now but it took work. I had to make sure I loved on them all,a lot more than usual. I also held my other dogs w/ Bitsy in one arm to let her know we all get loving here. I'd have her sit and wait her turn,just like the others. She's so much better about not being aggressive and growly. I don't know if I went about it the right way,Bitsy had abandonment issues,food aggression and issues w/ being possessive. I was actually getting nervous about Bitsy and worrying about her aggression issues. Seeing teeth bated was really scaring me..for the safety of my other fluffs and myself...
I just had to reassure her,she wouldn't be left out and I talked to her alot,using her name,touching her petting her. So far I think it's worked. Bitsy even kissed Sasha on her foot today while Sasha was laying on my lap.Any other time she'd growl if Sasha even laid anywhere near me or Bitsy. Sasha came up after Bitsy was already near me,laid down and Bitsy hardly paid any attention to her,that's big her her since the other Malts barely got near her and we'd see that curled lip,deep growl and teeth bared..... We got her in October so in the last couple months ,we've seen real improvement,it took this long to see improvement. Took about 5 months,before her aggression issues start to fade.
It's tough to pet everyone at the same time...4 Malts 1 Cocker and only 2 hands. I sit down w/ them a lot and they swarm all over and take turns getting loved on.