Complete rubbish left with badly damaged lawn.

Used the easy spreader a couple of days ago marked out my lawn with string so as not to go over any area's twice. Lawn has been badly damaged with black lines of scorched grass. Rain fell after application but not heavily. I think it would be better to just say water the grass after application don't rely on rainfall. Looking at the lines the granules clearly passed through too quickly at the start, but as the spreader emptied it left just the larger granules behind which did not pass through evenly with some holes blocked. So ended up with some lawn scorched and overfed and some either underfed or completely missed. Also if the product was a different colour instead of brown it would be easier to see if it is going on to thickly or unevenly. Had no problems with it falling apart but if it had I could have taken it back.