Calc Darling in the Franxx - Strelizia Apus vs VIRM fleet

The distance from Earth to Mars at their closest is 54600000km, or 54600000000m. Mars at it's furtherst is 401000000km away, or 401000000000m. The average distance to Mars from Earth is 225000000km, or 225000000000m, so we'll use those as our low end, mid end and high end.
https://www.space.com/24701-how-long-does-it-take-to-get-to-mars.html
Given the light is bright enough to visibly light up the Earth even through dark clouds during the day, then the apparent magnitude should be comparable to that of the Sun, that being −26.74 (though really it's likely even higher given it shone through the clouds easier than the sunlight did).
(Low end)
-26.74 = -26.73 - 2.5log((L/3.846*10^26)(146000000000/(54600000000))^2)

Breaking this down bit by bit...

(146000000000/(54600000000))^2) = 7.15023682
-26.74 - -26.73 = 7.15023682/((L/3.846*10^26)
-0.01 = -2.5Log(7.15023682/((L/3.846*10^26))
-0.01/-2.5 = (7.15023682/((L/3.846*10^26))
10^(0.004) = (7.15023682/((L/3.846*10^26))
1.00925289 = (7.15023682/((L/3.846*10^26))
1.00925289 X (3.864*10e26) = 7.15023682
3.89975317e27/7.15023682 = 5.45401959e26 joules

We'll hold onto that for now, let's do our mid and high ends.

(Mid end)

-26.74 = -26.73 - 2.5log((L/3.846*10^26)(146000000000/(225000000000))^2)

(146000000000/(225000000000))^2) = 0.42105679
-26.74 - -26.73 = 0.42105679/((L/3.846*10^26)
-0.01 = -2.5Log(0.42105679/((L/3.846*10^26))
-0.01/-2.5 = (0.42105679/((L/3.846*10^26))
10^(0.004) = (0.42105679/((L/3.846*10^26))
1.00925289 = (0.42105679/((L/3.846*10^26))
1.00925289 X (3.864*10e26) = 0.42105679
3.89975317e27/0.42105679 = 9.26182231e27 joules

(High end)

-26.74 = -26.73 - 2.5log((L/3.846*10^26)(146000000000/(401000000000))^2)

(146000000000/(401000000000))^2) = 0.132561365
-26.74 - -26.73 = 0.132561365/((L/3.846*10^26)
-0.01 = -2.5Log(0.132561365/((L/3.846*10^26))
-0.01/-2.5 = (0.132561365/((L/3.846*10^26))
10^(0.004) = (0.132561365/((L/3.846*10^26))
1.00925289 = (0.132561365/((L/3.846*10^26))
1.00925289 X (3.864*10e26) = 0.132561365
3.89975317e27/0.132561365 = 2.94184748e28 joules

For our final step, we'll get the timeframe to determine how long the light shone for.
3 seconds.

(Low end)
E = 5.45401959e26 X 3
= 1.63620588e27 joules
= 391.0625908221797431 petatons

(Mid end)
E = 9.26182231e27 X 3
= 2.77854669e28 joules
= 6.6408859703632888341 exotons

(High end)
E = 2.94184748e28 X 3
= 8.82554244e28 joules
= 21.093552676864244859 exotons

And on another note, given that Hiro doesn't wait around for minutes for the flashes to appear in the sky and they appear instantly, the VIRM explosions/attacks would be FTL.
4 seconds.

(Low end)
T = 54600000000m/4s
= 13650000000/299792458
= 45.531499 C

(Mid end)
T = 225000000000m/4s
= 56250000000/299792458
= 187.629804 C

(High end)
T = 4s
= 401000000000/299792458
= 1337.59202 C