is it a must to cut it?

[92Miata]

Problem being though, his lights didn't increase. They actually decreased.

Op stated his original lights put out 400+ par. New lights put out only 300+ par. Thats a 100+ par decrease not increase.

Par is a rough equivalent of PUR and not itself all that useful when dealing with spectrum changes. Green and yellow and red produce lots of par, but aren't used much by corals.

He switched from a cheap light to an expensive one that most likely had a much more precise spectrum and saw behavior typical of corals being exposed to high light. Horses.