Moldy bud typically is fairly obvious w/ some close observation. Borytis is the most common bud mold. This looks like brownish/greyish areas that usually have more effected areas deeper within the bud. More advanced stages can appear white and fuzzy. Is your humidity high? This is the most common cause. A filtered intake can help also. Bud mold and and stem rot can spread rapidly. It must be cut out - all of it - every last bit. And the room temp and humidity should be lowered. The resourses section in this site will tell you more. Best of luck......