Getting Weaker?

I lost 50lbs on my incline bench and 35lbs on my rope pull downs in 1-week. Could this be possible?

I expected a drop of weight in my incline due to me putting this exercise second after pec decks. But that still seemed like a lot of weight for me to drop in a week. I have to attribute the additional loss of power to different machines. I pressed 250 easily on the Hammer Strength, but I only did 200 on another machine that had cables. So the weight on these machines isn't quite accurate. Also, I did feel a difference in the angle, so I'm sure that also had a lot to do with my power outage.

I then did rope pull downs 1-week with 135lbs for 8 reps, then could only manage 100lbs the next week on another machine. Again, I could not believe that I lost that much strength so I went back to the first machine and could easily lift 135lbs for a few reps.

So, machines make a difference, both in weight and in angles. However, I would have never imagined this big of a difference and am a bit disappointed. I mainly use machines because for the most part, I don't have a training partner so I cannot safely hit failure. I guess, for the sake of tracking, I need to use the same machine every time I workout. Otherwise, the weight discrepancy will not allow me to properly track my progress.

I don't care about how much weight I use, I just want to be able to track my progress. The difference in each machine just makes this task more difficult, so I'll have to wait if someone is using the machine that I'm tracking my progress on.