I could see how being lighter would affect the lat pulldown, because of the way it works...being lighter and smaller, it would just be harder to stay in the seat, lol. You might switch to pull-ups/chin-ups there. As far as strict pressing or free weights, though, you shouldn't be getting weaker. Like another poster said, taking any time off at all can set you back, even being off sick for a few workouts, but you should gain it right back after a week or so, for a short absence like that. If you've been doing the same old routine for a while now, try changing it up. Go heavier for fewer reps, and/or change out the exercises you're doing. If you've been all on the machines and cables, try some free weights. If you've been doing straight sets with the same weight every set, start adding weight each set and decreasing reps, or otherwise just change it up. Your muscles need some "shock and awe" every six weeks or so, at the outside, to keep them growing and getting stronger.