I am afraid other members are quite correct here (afraid because of your situation, not for the other members' sound advice).
Mikrogeophagus ramirezi is the common or blue ram, in any of several varieties selectively bred, and it must have warmth. A temp of 80F/27C is absolute minimum, but the fish will be better a couple degrees higher. None of the other fish mentioned can manage in this.
You mentioned that you had this species previously in cooler water...but I can guarantee it did not live to its normal lifespan. Fish are ectothermic, so the temperature of the water governs their metabolism and inner physiological functions. Fish requiring warmer water have evolved over thousands of years and it is mandatory for their normal health and lifespan functions.
The other fish in your tank have serious issues with insufficient numbers for the shoaling species, and then there is the space issue. I'm sure several of our members would be willing to sort this out if asked.