Welding Tips and Tricks

I have been working at my first welding job for about 4 months and i started off on 2 different welding machines, now i am on my third which is a millermatic 251 pretty much exactly like the first machine i started on. I started off welding pretty well on the first machine with some noticeably good welds. My wrist started hurting 2-3 weeks ago and i started taking it easy. now when i weld it looks like garbage (most of the time) and i cant seem to get back into the groove. I keep messing with the settings/chair height/pretty much anything i think will help and nothing seems to work. I do think this machine i am currently on is not as good as the others or i am just incapable of setting it up. It is really embarrassing because i do have an associates in welding and fabrication but i was insanely out of practice when i started the job. The material we are welding is 3/8's hot rolled plate with 1/4 inch angle iron welded to it to make brackets. as i stated before the machine is a millermatic 251 on 75/25 argon/co2. Anyone's insight into what might help is greatly appreciated. attached are some pictures. Top pic is earliest, middle picture is latest, and bottom picture was somewhere in between.

Not sure I understand, so I'll ask: what exactly about those welds do you dislike?

Well I think the top and bottom are acceptable, but the middle image isn't. Undercut, inconsistent looking, etc. Something changed and I cant put my finger on it. Maybe some insight as to what settings someone with the same/similar machine would run for this mix of materials. Machine is a millermatic 251. I am running 70/25 @ 30-35 CFH, .035 er70s6, @21.4 volts 316 wire speed. Thanks.

The change was likely you. Your travel speed or gun angle. I’m betting travel speed.

by the look of it, lack of cleaning before welding.

Thanks for the input guys, is there any thoughts on my machines settings? I realize all welding machines weld a bit differently but i am just looking for any input that can give me an edge.