Creatinine was 1.0 and GFR was 61 in janurary and in july they are 1.12 and 51 should I be concerned. Donated a kidney june 2008?

Possibly. Gfr is the fluid flow rate between the glomerular capillaries and the bowman's capsule. Gfr just below 60 indicates very mild decrease. Important to have levels rechecked, eat healthy and stay away from medicines and conditions such as massive protein break down taxing the kidney.
Yes. Talk to your pcp.Reevaluate your medications, control your blood pressure, diabetes and cholesterol.Avoid medications like nsaids that can renal function worse.