separation problem with GelRed

[apolll]

Hello!

We recently switched from ethidium bromide to Gelred in our lab. (We always prestain gels - poststaining is no option because its too inconvenient and timeconsuming - using 1xTAE buffer).
Our DNA samples and the ladders aren't separated as sharply as it was when we used ethidium bromide. I already have some ideas what to try to improve the separation (using TBE buffer, using 0.5x buffer, applying lower voltage, etc.)
Since I optimized several methods in the last months, I am really tired of it and I just wanted to ask you if you had the same problem and if you have found a solution for that or if you have any advice on what to test (first)?

Thank you for your help!

[canalon]

I am a bit surprised here, you say that post satining is too time consuming but you are ready to slow down your gels. It takes 10 minutes for staining, and about as much if you want to destain, which should not even be a problem with gelred. So why not post stain?
If this is really not an option, lowering voltage is usually a good start. And re-using buffer less.