Happens to me ALL the time... At this point, Ive simply gotten used to seeing the tint... My pool fill water is via a well system.... When my FC levels hit the 6-8 range, the tint returns,,, when the FC level drops, the stain disappears... If anything, Ive noticed that keeping my PH Levels on the low side helps a bit (7.2-7.4)
But try this:
When the pool tints, grab a Vit C tablet and simply rub it on the side wall of the pool....if you see a stain disappear (it will be instant), you're dealing with a metals issue...