Or are they also getting more of the supplemented ffs as they are closer to the top and the ffs run up?
Nope, frogs feed mostly off the bottom of the tank. However, the males are up in the plants more while the female is always hunkering around the bottom. The female is much paler in color.
Potentially because some have complained that "you will never get the real bright red like wild caughts." I believe Corey supplemented the frogs from tadpoles (however, no astaxanthin) and said this.
It could just be a supplement thing in general, but also most do not use UVB over our anurans.
this probably is a false correlation (for frogs), but doesn't the redness or orangish coloration deepen for goldfish/koi in outdoor ponds due to UVB exposure? (other than supplementation) Many books state that.