In addition to VTA, VTF and break-in, another possibility is the loading of your new cartridge.
The Pro-Ject Tube box gives you three impedance loading options on the MC inputs, 100, 220 and 1K ohms. If I were a betting man I'd wager it's set @ 1K. Try dropping it to the 100 ohm setting. Try all three settings for that matter. It won't do any harm.
BTW, I'm only *assuming* this Nottingham #1 cartridge is an MC. I've never heard of that particular cartridge, or even that Nott' made cartridges at all. My guess is it's a rebadge made by one of the regular cartridge manufacturers. If it came with any specs those might be useful to know.