Qualifying on Saturday went well for Fisher who finished the session in fourth place and started the first of three races from the middle of the second row.
As the lights went out he settled into fourth place and became embroiled in a battle for the lead.
But as the race wore on the top three riders made a break leaving Fisher to battle it out for fourth place.
On the penultimate lap he briefly made it through to fourth place but by the time he got to Redgate on the final lap Aaron Silvester had regained the position and Fisher followed him through the lap to take the flag in fourth position.
Starting the second race from the second row once again Fisher didn't get the best of starts and found himself down in sixth place on the opening lap.
But by lap eight of 14 he passed Jack Bednarek and held station through the remaining lap to take fourth place.
In the final race Fisher was again involved in a battle for the podium throughout the race and finally crossed the finish line in fifth place.
Meanwhile Whitmore-Wilson qualified in 11th place and began the first race from the fourth row.
He was involved in a fierce battle within a large group of riders and completed the 10 lap affair in 10th place.
The second race over 14 laps of the Donington Park Nation circuit went much the same way with Whitmore-Wilson again battling for position within a group.
This time he crossed the finish line in 12th position.
The final race of the weekend brought Whitmore-Wilson his best result as, after fighting his way through from 13th to eighth, he just missed out on the position when he was beaten by Lee Wells and had to be content with ninth position at the flag.
This set of results means that Fisher loses the championship lead but with 145 points is still in contention in third place. Whitmore-Wilson remains in fifth place on 74 points.
The next round is at Croft in North Yorkshire on June 11/12.