Duff indicators?

Hi, first post in a while...
Seem to have a problem with my indicators.
I have just finished my diy rear bumper with built in lights (tail/brake, indicator and reverse) and I successfully wired them all into the original harness. When I say successfully, they were all working!
A day back on the road, 25 miles or so, my indicators have stopped working! Everything else still works including the hazards, which is strange but to me confirms it's nothing to do with the wiring.
Still seems a bit of a coincidence...
I can't seem to find a fuse for the indicators, hazards yes, indicators no.
I'm suspecting the flasher relay is at fault but that's only a hunch.

Could it be thre size of my new rear indicator bulbs? I went for 21w. Could that have overloaded the flasher relay?

Anyone else had their indicators stop working?