You don't have a "low squat", you have a low everything. You should also check the way you deadlift, I suspect you might be deadlifting with rather improper form (lower back rounding) which is why there is such a huge difference so between your squat/deadlift so far. Either that or your leverages are very advantageous for the deadlift and disadvantageous for the squat. If you're really worried, post a video of both your squat/deadlift. As for the rate of increase, I'll just quote Jim.
"Each lift will NOT increase at the same time. This is normal. Keep plugging away. The breakthrough will eventually come." - Jim Wendler