Genetics, not a virus.
Plants generally grow normally after a while....3 leaflets instead of 5 is not an issue.
I have grown many plants with mutated leaves, it does not seem to affect yield, potency or growth noticeably, however, in my opinion, life is too short and electricity too expensive to grow "maybes" and cull any seedlings that are strange.
The leaf issues you are worried about do not occur due to reasons of nutrition in my experience, it is usually a flaw in the plants genetics. Whether you are happy to grow a plant with flawed genetics is a decision you will have to make.
Not all seeds are destined for greatness, some just don't make it....that is why you should always plant more seeds than you think you will need, in case of duds.