Chest exercises.

Comment Deleted by Article Creator

No. Are you trying to do the push ups a day or two after you've trained your chest?

If your training for strength with low reps it would effect stamina,remember strength training and endurance training are different things.of course a weight gain would effect a bodyweight movement like a press up,have your shoulders gone stronger or weaker??

Stronger, reckon its a muscle stamina thing.

Cant say I've noticed this but tbh Ive not tried to do push ups in a while

I think it's no doubt your weight gain that has effected it.
8kg increase in bodyweight is a large amount,and if you have not constantly been doing push ups,your muscles although stronger,are not conditioned to move your bodyweight.I think if you kept doing them while you gained weight then you might not have seen a decrease.

Not sure mate, although when I workout chest I do bench press (with dumbbells) immediately followed by 10 pressups for 3 sets. It hasn't really effected my pressups and I bench as heavy as I can, which is around 50kg.