I bought a 3 pound bag of peeled garlic. Some of them have white mold on them. Should I throw the lot away or pick through the bad ones & discard?
Pick through. I even cut out, then use the good part. It is most likely Penicillium hirsutum, "blue mold of garlic". Sporulation and germination are delayed at low temps (i.e. fridge), therefore you see only white which are the mycelia.
 "Low-temperature biology and pathogenicity of Penicillium hirsutum on garlic in storage", P. Bertolini et. al, 1996, https://doi.org/10.1016/0925-5214(95)00025-9