Hiya and Welcome Smallo.

Try dropping the "[target=focustarget]" from your main toons macro. With focus target, the reason you may be getting this error is because your main is setting himself as the target's focus, thus causing your alts to target your main as the "focuses target"....sort of. (If that makes sense. )

Hope this helps.

Edit: Now, that my brain has registered what you wrote... :s ..With [target=focustarget] on all 3 macros, your alts aren't automatically assisting your main because your setting your main as the focus with your alts and then trying to cast a harmful spell on him. Set up some sort of assist command for your alts to target what your main has targeted.