With 250k pots, things should sound even 'muddier' with more treble roll-off, though there's probably a different reason for things sounding muddy, and maybe damaged pots from overheating if the soldering is as amateur as you say it is. Are the pickups ceramic bar magnet on the back types, or alnico pole piece types? You haven't shown any pics of the back of the pickups or the wiring harness as far as I can see.