I suggest you try some Ajax dish detergent instead of record cleaning fluid, then rinse the record thoroughly, vacuum it and further dry it with a microfiber terry towel as you did.
Most record cleaning fluids are isopropyl alcohol-based and are solvents. Detergent and soap are surfactants. Whereas the solvents try to dissolve the gunk, surfactants make the gunk unstick from the record groove. In my experience the detergent works better because--especially on very dirty records--the solvent can't dissolve all the dirt whereas the detergent can make it unstick from the record.
GIven that LPs are made of polyvinylchloride, a very tough substance, could it be that your cleaning regimen moved gunk into the high treble groove modulations, and that a second cleaning might fix that? BTW, those microfiber terry towels have 80,000 fibers per square inch, plenty small to get into the groove and help pull things out.