Coolant Leak/Poor Run Cold

I have a 2001 Mazda Millenia that runs really poorly cold/first few miles (has gotten worse with time) and is leaking antifreeze (green fluid down back side of engine). I thought it may be a head gasket but in beginning to dis-assemble I found a fitting on the back side of the manifold loose. The fitting is fastened to the intake manifold with two larger bolts, has two 7/8" hoses attached to it and it is the same fitting that I removed a while back as part of an EGR port cleaning process I performed. Do you think this fitting being loose could be the cause of the poor run and/or coolant leak? The hoses are not leaking but the fitting was likely not tight enough for a solid gasket seal. Thanks, Mark