It's pretty normal to feel tired by evenings. Feeling irritated is different though. Find out the reasons behind your irritation. It could be due to physical tiredness, lack of good diet, overstimulated mind (high caffeine, high anxiety), exhausted mind (too much time spent on kids/household), monotony of routine, hormonal issues, etc
You may want to take out time for yourself (which is difficult with 2 children of different age groups). Anything that interests you needs to become an important part of your schedule.