De vere Dichromat 504 Colour Head (contrast Problems)

The model I have is the MkIII , just started printing with it , straight print fine for exposure. I dial in a filter value and my highlights take on a grey hue, im using a variable contrast paper taking filter values from Ilford site under the kodak headings, Im aware this is not gospel but the wife wants to see a print (you know what I meam)ahem! and I cant seem to get anything passable.I have noticed some comments regarding VC not very good over grade 3 values might I be experiencing this.

I have used negatives which have printed very well on my old enlarger at the selected grade I have used this for comparison.

Rgds

There are three things to check for. First, are there any light leaks from the enlarger? Second, is the mixing chamber diffusion screen or lining yellowed? Third, are your dichroic filters faded, especially the mageneta? After getting new filters, my max contrast went from grade 3.5 to grade 4.5, a significant jump.