dystrophin

I have a neat dilution on my dystrophin 1 and 3( novocastra) and after alexa 594, the flourescent stain was excellent however after three days or a week the stain starts to fade out. My dystrophin 2 in 1:3 dilution in PBS remains the same(meaning the stains still looks excellent). Can somebody help me figure out how can i remedy this. I hope i can find the answer by diluting it with PBS but the stain is not sharp enough. would it be on my rinse? Thank you for your help.