I'm having similar problems on my 1400 too. The test print shows about 40% of the Cyan.
I have reinserted original Epson cartridges and the test print was fine. The CISS system is new ( the ink tanks that I fill up aren’t new though ). I have sucked the Cyan cartridge and it’s constantly 'bubbly'. So, I added new ink into the CISS Cyan cartridge and the test print was the same.
So I’m guessing it’s not the printer as the original cartridges printed fine. The CISS system is new. Could it be the ink tanks?
Any help would be appreciated.