How should I time my weight training in my swim schedule?

I currently swim 6 sessions per week (Mon Tue Thu Fri morning, Tue evening, Sat afternoon, with 2 rest days (Wednesday and Sunday). Recently I have added weight training into my routine, and I would like to do it for 4 weeks. I have currently put them on evenings Monday, Wednesday and Sunday last week (45 minutes each season), but after my weight training, I feel my muscle stiffness and tightness (especially my pecs) sustained overnight, sometimes affecting my swim training as well. Am I putting my weight training to inappropriate times, or should I sacrifice some of the swim sessions for that? (I am using a progressive overload schedule for my swim training, gradually increasing my training mileage, but that does not include any weight training which I never had before)