it is completely normal to fight over treats
mine do it all the time and they love each other, I am glad things are improving.
To train them together is difficult but not impossible and it could be good so Willow could learn from Mylo.
I train mine separately and also together usually Laska gets over excited and gets in the way, if he is like that I tried go keep him busy with a treat in my other hand, in the begging tho it was more difficult because they didn't knew their names very good.
Another thing I do also, with tricks they both know very well is to make them do the same trick at the same time and use both hands.
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