Just some thoughts:
Take the fish out that has the large things on its tail and see if you can see that they are some sort of parasite. Try to pull one off. Parasites have only one point of attachment (the mouth) so some of what you see should come off of the fish though still be attached to the fish. If so, you could treat with saturated salt solution, I can give you my article on that treatment if you want it, or you could use any of the meds that treat for parasites.
If it is not a parasite, it is most likely just a fleshy growth that should not greatly affect the fish or it longevity even though it does not look too good. Fatty growths can be the result of a fatty diet. You could try feeding a lower protein diet. Your fish may need a higher fiber diet.
One other thought, many fish particularly swordtails and platys are quite prone to getting tumors. In fact they are studied at some research places for this reason. I guess it is possible that these growths are tumors of some type, benign or malignant. Again, I do not think they will affect the life of the fish much, though it depends on where the tumor is. Tumors in livebearers are almost always seen in the older fish, though not all get tumors.