I can't really help on that. I don't use LED's. I am an electrical engineer so I am interested in trying them but I have top of the line HID equipment. One of these days I will get some LEDs to mess around but I don't need them today.
I have used Mylar and that works for maybe 2-3 grows before it is real bad and needs to be changed out.
One Big thing in indoor growing is efficiency. If the light is reduced by 10% then the yield is reduced by 10%. Now we are talking about reflected side light so not as big a deal but anything you do that is less than optimal means you have to adjust your recipes and plans.
For example you may find a journal where someone ran the same strain as you and they are using the same medium (lets just say for arguments sake you both are running the same identical off the shelf RDWC system). But they are using a larger space with more accurate climate controls and better air flow and 10 % more available good lighting. You can not follow their program exactly. They are running a more efficient room that will have more photosynthesis with faster more vigorous growth. So when they say on week 4 they upped the PPM to like 700 and it just barley started to show signs of burn...if you did that you would have substantial burn most likely.
So just understand (myself included here) that when we build up a micro garden setup we have already put major constraints on ourselves that prevent us from growing ideal plants. We have to do what we can to optimize the space we have and get as close to an ideal as possible and compensate for all the things we can't or don't get right. Usually that means lowering the nutes down by a non-trivial margin.