I recently also added a brown flesh/green mouthed trumpet to my tank. It came from a low light tank. In my high light tank (about 8w/gallon) it "inflated" for a couple of days than turned white and didn't inflate for a few days, just bare skeleton. I have to be really careful with LPS
's in my tank as I have baked a couple from being too high
I thought it was dead because at night white stringy tentacles that looked more like spaghetti worms would extend from the edges and I thought it was dead flesh (not feeding tentacles from the mouth like normal). After about a week, it started to inflate a little but the flesh was clear'ish. Now it's inflating well but it's much lighter brown than originally. More like a peach color. Like it morphed in a high light tank. After about a month of "healing" it's began to form dual mouths on a couple of polyps.
Sorry for such a long story, just enforcing "newfound77951" statement on how they can react in different lighting.