If any of you is struggling with jealousy issues, maybe these help:
For basic communication and solving conflicts, maybe these helps:
You may very well enjoy polyshipping in general... but not with these particular people specifically.
Again, you cannot carry the load for a 3 people thing alone. A 3 people thing needs all 3 people putting in effort. If they are not willing to participate in relationship together with you in healthy ways and they continue with less than loving behavior? You may be better off withdrawing your own participation and being free of these people so you can attempt to polyship with people who are more compatible/have better relating skills.
Only you know where it is at because you are the one there.