Slight musty smell on buds 4th week of flowering

About a week ago I had mainly covered my exhaust vent( but still was able to blow air out)to block out sunlight and when They woke up I noticed a musty smell in the tent and the rho was at 60% and now I smell my buds and some of them still have this smell and I'm wondering if I should be worried about mold. Before and after this incident I kept my rho around 30% and temp 75. I have two fans circulating air in there
 
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