Changed lights - old fish now fighting

[Shy_Koi]

I have a (mated) pair of 12yr old clowns, that have been best buddies for over a decade. They've always hung out peacefully, together in their cave, rarely venturing far. No other fish in the tank. No additions in years.

Changed my lights from T5's (2 x 54w) to LED's (IT2040) last night.
This morning I noticed that the pair were separated in the tank. The smaller male is being quite aggressive towards the larger female and keeping/chasing her away from their cave. She looks pretty lost at the front of the tank...

Over the years I've changed from CF to MH to T5, as well as changing tanks (and a house move), and never any problems with this pair.
I have an awful feeling that I'm going to lose my old female.
Looking for some advice, please. Do I need to pack up the LEDS?


Tamara