An effect due to fusion born triton production has been observed in JET high-performance deuterium plasma discharges with NBI and H-minority ICRF heating, using DD and DT neutron spectrometry as well as fusion product loss measurements. The observations show that increase of the triton burn up rate leads to decrease of second harmonic ω_cH = 2ω_cD enhancement of DD neutron rate and an acceleration of tritons due to absorbing ICRH power at the third harmonic ω = 3ω_cT. This effect indicates a redistribution of ICRH power absorption at ω ≈ ω_cH = 2ω_cD = 3ω_cT towards increase of triton concentration at the ion cyclotron resonance layer. It determines the necessity to consider the ICRH power absorption ω = 3ω_cT in modelling of high-performance deuterium discharges with simultaneous NBI and H-minority ICRF heating for development of DT plasma scenarios and fusion rate predictions.