Your best off removing one of the clowns as stated. The clarki has taken up his territory and he wont give it up. Mixing clown species in smaller tanks causes many problems, especially when start introducing nems. Also condies are not natural hosts for clowns so the chances of both hosting a seperate nem is slim to 0.
Only other option i can see would be to remove the nems and hope no more disputes take place. Introducing BTA's at a later time could yield different results.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.