Correct usage of lagging behind/falling behind/deficient in

I am lagging far behind my regular work schedule. [correct. You imagine yourself on a line of time, where you are finishing later than your planned times]

I have been repeatedly falling behind with my work. [correct. Perfect idiomatic usage of falling behind with, imaging yourself in some sort of race with your tasks, in which you keep falling behind them]

I am falling behind rest of my colleagues. [should be “... the rest of my colleagues”, indicating that you refer to the group of all your colleagues. If only some were ahead of you, say “... behind some of my colleagues”]

Deficiency is a shortage.

Today I resulted in a work deficiency of 2 hours. [I never heard this construction, which is at least confusing. A work deficiency sounds as if you did less work rather than late work. Most will consider this sentence wrong]

Today I was deficient in 2 hours at my work routine. [This too sounds as if you are trying to say you did less work rather than late work. Most people will not understand it. Most will consider it wrong]