Tax on the trust income due to plan disqualification; do all earnings of the trust turn taxable, not just those earnings traceable to the contribution

[Guest Enda80]

Tax on the trust income due to plan disqualification; do all earnings of the trust turn taxable, not just those earnings traceable to the contribution made in the year where disqualification occurred? What official citation would support this?

I do not refer to a case of a rollover of unqualified assets, but a case of losing qualification due to other circumstances.