Battery Tray

I popped the hood today to wipe down my engine bay and noticed a watery yellowish brown liquid in the part of the battery tray that is not covered by the battery. I pulled the caps off and the battery does not appear to be low in any of the cells. It appears that whatever that is has been going on for awhile as there is a film from behind the headlight all the way back under the fuse box as dirt is stuck to it. Do you guys think that is regular rain water collecting in the tray or have you noticed it on your trucks? Thanks for any input.

 

Battery isn't low, it is probably rain / wash water.

 

Picture

 

Thanks guys, I was leaning towards some rain/water buildup and I didn't think to snap a pic cause I started drying, wiping, and waxing all around.