Stuck with two of the horsemen paintings

[Airtamis]

I've got 80% of the truth discovered, opened all of the memory boxes, but I'm stuck with two of the horsemen painting and three cubes.

I have three cubes - MNOPQR, ABCDEF, and then YZ and some greek letters.

The two horsemen left are MORS and Bellum, Mors in all caps missing an M and Bellum with the letters reversed missing the B. Logic from solving the other two make it seem like I should put the M in Mors and the B flipped into Bellum, but they will not take them. I've also tried using the Beta from the Greek block into both of the paintings, but it doesn't go in them either.

Is there anything that I am missing here? This one is getting frustrating

[Nixmachine]

I'll spoil the first part, MNOPQR cube fits Bellum, ABCDEF fits Mors

[Airtamis]

Ah hell, I found the ABCDEF cube last so I was already fried by this point, but the lowercase b's a real trick. Thanks for the help

[SONGMJ23]

YZ is not for the painting. Find somewhere else in the chapel to fit.