PA-28 pilot reported loss of RPM's during a touch and go and made a full stop landing instead.

Narrative

Prior to takeoff I did a run-up; most unusual thing was both mags ran a bit rough mostly the right magneto. I cleared them out by selecting one at a time then leaning the mixture a little near half and added power to 2;000 RPM for about 15-20 seconds. Both sides were clear and smooth 50 RPM drop. I proceeded to takeoff and all was green and normal. I practiced my Commercial maneuvers for proficiency. Steep turns; Chandelles; steep spirals (did not exceed 120 kts indicated and did add grunts every few seconds and full maneuver was done for about 20 seconds and was performed once and did not exceed 125kts to not super cool the engine); engine out and short field pattern work. During the Chandelles I felt some sputtering for a few seconds at full power but later never came back. I came in to do a short approach simulated engine out at ZZZ followed as a touch and go. Next would be a short field landing also touch and go. On the third landing also a short field about 100 feet right before the runway I got spitting and what seemed to be a loss of RPM I added a bit of power more than I usually feel I need to keep me going. Upon landing I proceeded as a regular touch and go adding full power slowly and having no flaps. After a few seconds upon reaching full I had very large sputters followed by a loss of RPM of about 1000 going to about 1300RPM. I immediately reduced power followed by gently braking and full elevator back pressure knowing I had plenty of runway and excessive braking was not required.