Mudguards

Some - but the quantity and direction of streaks and splashes suggests most comes from the front and below?

A front mudflap is being contrived over the weekend...

If your mudguard isn't close to your tyres, the the murk will get out easily as well, as for the front mudflap, make it as long as you can, picture below illustrated what you're referring to;

Alternately you can just get the SKS mudflap and put it on the rear;

Went on a wet ride on the Surrey Hills, no more murk to be found under the BB.