There's no publicly available information stating that either Gwinnett Tech or Athens Tech specifically accept Cornerstone Correspondence Diplomas for credit. Each college has its own admissions policies and procedures regarding the acceptance of prior learning, including diplomas from other institutions.
To find out definitively, you must contact the admissions offices of Gwinnett Technical College and Athens Technical College directly. They can tell you whether they will accept your Cornerstone Correspondence Diploma for course credit or if it can be used to fulfill any admissions requirements.