I've had similar issues using 28g wire in my kayfuns. I was running 1.8 ohm compressed micro coils (2mm ID) 12 wraps and have since gone to 7/64 id 8 wrap open coils and it cleared it up for me. If your making tight compressed coils stop. I found that the juice and wicking in the center of a tight coil will burn and cause a harsh vape with a fire like sensation in the back of the throat. On the mini's I wouldn't use anything thicker than 30g personally and no less than 1.8mm id or 1/16 inch. Contrary to the micro coil fans, you don't need to compress a coil to get good even , center out glowing. they just need to be pretty evenly spaced wraps.
Thanks for the pointers I will try building an open coil with 30g.