Correct vetilation is key after cleanup.

My house is only 1000 square feet. Currently there are two square passive
vents near the top of the roof and there are two gable vents on the walls on
the sides of the attic. One article suggests that having both types of
vents is bad. I'm just wondering if anyone disagrees with the idea that
both types are always bad.

Anyway, it's strange how the problem is mainly just on the sheathing on side
of the attic (the side in which the roof has less exposure to sunlight).
That side had a leak in one area around 9 years ago, before I had a new roof
put on, so I'm wondering if it's possible that the mold there now is a
result what happened back then, or perhaps the mold started growing back
then but gradually got worse over the years. Right now it's noticeable but
doesn't seem really bad at this point although I fear it will get worse.

Snow can temporarily cover up the vents at the top of the roof, and I wonder
if this contributes to the problem. I also wonder if my bathroom's lack of
a fan contributes to this problem, since moisture from taking a shower could
potentially rise up into the attic.

Anyway, the main question is what type of expert I should call to fully
diagnose and solve this problem. (general contractor?) I'd rather hire
someone then try to take care of the problem myself. Let me know what type
of specialist you recommend I call.

Thanks.

Jeff