No worries.
Your diet seems fine if a bit low on the calories front, but the question is: are you gaining weight? If you're gaining weight at stalling, I've heard a rumour this suggests you're putting on fat rather than anything interesting... functionally, that makes sense, but...
Secondly from a strength perspective, this will vary day-to-day: I just squatted a 1RM two days ago, but that doesn't mean I'll be able to hit that today or tomorrow... this is entirely dependent on your diet, sleep/recovery level, circulating hormones at the point of lifting (cortisol, prolactin, testosterone to name a few), etc. However, you're lifting sub-maximal (8 reps) so this would suggest you're not recovering (sleeping/eating) enough - from a purely simple/basic perspective.
Thirdly, when increasing weights, progressive overload is key to any strength/size regime, and there are as many different ways of approaching this as there are weights in the gym:
1) Use a popular routine (Stronglifts, MadCow, HST, etc.);
2) Increase the weight for your exercises by 2.5kg per session or increase the number of reps you bang out. If you're failing to complete, then either eat more or drop the weights and take a "volume run-up" as such (this involves more reps/sets at lower intensities, slowly building back to more of a strength approach with lower reps/higher intensities);
3) Go by feel: if a set of 8 feels easy, increase the weight until it feels ahrd...
This is where structured routines like 5/3/1, Stronglifts/whatever are very useful as they "do the calculations for you."
Finally, don't use the smith for anything. At all. Use a power rack for benching if you can. Failing that, use dumbells. This might sound like gym snobbery (and it is, I suppose, to a degree) but there is a pretty good reason:
- Taking any of the instability out of a lift (by using a smith) takes the functional strength component out of it. It also reduces the stabilising muscle activity out, too, reducing the hypertrophy potential.
- You will never actually know how much you're lifting. As a gym brofessor has once said: "nobody actually knows how much the bars on a smith weigh..."
So, things for you to think about:
1) Eat more;
2) Change your routine to either an established on for progressive overload, or shift to your own feeling of what works (I would strongly suggest an established routine like either MadCovw, 5/3/1 or Stronglifts).
And you're not going to get huge. Not by a long shot, so don't worry.
