Is it just the lower buds?
Top and lower
Where is your fan placed? Often times too much air blowing onto the plant will do that. Some pistils turning brown in early flower is normal but it shouldn't be throughout your entire plant.
The fan is placed to go over the top of the canopy. its a small tent so it might be the stress from the air. i have the fan on high, its a 6” oscillating fan and it moved them around quite a bit. Less air movement you think?
@TheGanj I would say most likely. A pic of your whole plant may help tell us something.