Duarte road bike - Made in Colombia

Okay so I’ve ridden the frame a bit, and the mud and crap is ruining the paint on the seat tube as there is a gap of only 1mm. Basically I have to run a 23 or less tyre. The frame is lovely to ride, but this is fucking stupid. Am I missing something, or did the frame builder fuck-up? As I said the frame has only vertical dropouts so unless I machined them out a little, there is no adjustability.
Not happy.
Have you got any ideas on a fix?

Got a great training bike, pity I have to run 19mm race-only tyres yay!