Black ink not printing any more

[Islesart]

Had my Epson Workforce printer for a couple of weeks. Printing was great and was really happy with it. Last week the black decided not to print fully any more. Colour was a dark grey and spotting in bits. Cleaned the print heads via Epson and used a cleaning solution to no avail. Left the solution on print head over night one night also - still the same. There was plenty ink in the cartridges during this. Contacted supplier next and they sent me out a new black cartridge - still the same issue. I was then advised to download their software to perform an ink charge - completed this. Still same issue. The supplier then said I must have burnt out the print heads and would need a new printer! Bought another printer at Argos today. Set it all up again.....same issues :(.
Have done another ink charge, ensured cartridges are full and will leave overnight. Unfortunately though I have only a handful of mugs to sell at a market stall tomorrow. Completely stumped. Can anyone help? Thanks in advance

[Islesart]

I also called Epson. Was told to run 6 print head cleans which I have done

[pw66]

What design software are you using? Could you be outputting your designs to the printer in a CMYK colourspace when you should be using RGB?

[Islesart]

What design software are you using? Could you be outputting your designs to the printer in a CMYK colourspace when you should be using RGB?

Good question. I use Photoshop and I will need to check this. Thanks for your reply