Some years back, I volunteered to help resurrect a local high school's darkroom. It had gradually become a storeroom and after clearing it out, I was happy to see that it was equipped with decent equipment (Beseler 45XL's, MXT's and a few 23CII's) that were fitted with 6 element Rodagon and Companon-S glass for all formats. Our first actual printing session left me disappointed with flat results as you described. I'll spare you the trouble-shooting details but it turned out to be an almost indiscernible slight haze in the lenses. A quick initial exam of them had me thinking the optics seemed new appearing. A bright light, careful exam allowed it to be seen. I brought a known optic from home and the issue cleared up. It was such a subtle amount of haze that at first, I couldn't convince myself that it could have the dramatic effect that it did.