Minimum recommended mppt string amperage ?

Had a strange occurrence today storms rolled in and it got really dark I was checking something on my 18k pv inverter and noticed my #3 string producing 20-25%more power than #1 now were only talking 60w to 75w witch is nothing but got me thinking.
18k nppt inputs 1-2 bridged 25a inputs 3 and 4 _15a each I have a single string of 12 panels on input 1 and 6 panels on input 3 panels are 32v nom. 8.5a. it was afternoon lighting was equal all panels are new fresh off the pallet. This is definitely not the case in normal production but enough to get me thinking of moving array to #4 input to see if I get better low light scavenging.
Any thoughts?

For the sake of science and testing my theory I moved the larger array from the 25a mppt input to the 15a mppt input and watched the inverter display from first light till I was satisfied with my data grabbing a screen shot every few minutes or so and checked when storms rolled in later in day.
My conclusion is it definitely makes a difference in low light conditions but inconclusive in full sun.
Now I did not small arrays input only large one and no the yard light wasn't affecting results I tested that as well.
Sorry I didn't grab a screen shot of the before stats can easily be changed back to prove concep but for now I plan to leave it this way for obvious reasons. In near future I'll be building a permanent array of 10s 2p for mppt#1

Do the 15 & 25 have the same voltage working range?

Yes

Just because I know someone is going to ask

Just thought I'd share my findings with others