iPhone 5C Issue

So I just got refurb iPhone 5C. It does have a warranty, but I have issues with battery life, heating, etc. So I called Apple today, they did a diagnostic. Their systems shows that my update and restore from two days ago shows it won't be a software issue. They think my phone is fighting itself with access memory or the RAM to run apps. So it works twice as hard to work with apps even though my phone doesn't use background refreshes or location services much. I don't use many apps either, but I do tend to leave them open from time to time.

What my question is that has anyone heard about the iPhone RAM chipset giving out within a year of the phone's manufacturing date?