Help! Lemon Tree Loosing alot of leaves

Hey ive had this lemon tree for about 2-3 years now and repotted it last year.
Were experiencing quite a bit of hot weather in ottawa atm and im not sure if this is due to too much watering a lack of nutrient or root rot
thanks in advance for anyone that can give me a little bit of insight on whats going on in my lemons trees life

idk why their all curled upwards, praising the sun?

Well… a good rule of thumb when you pot up is to go only up one pot size.  There is a tendency to over water if we put a small plant in a big ol pot…we get all that soil wet and things go badly.

General yellowing followed by leaf drop can certainly be caused by over watering.  At some point the plant is actually unable to breathe with its roots ( my best way of saying) and kinda drowns.  At that point it’s not unusual for leaves to yellow and fold with stress. And drop.

If you gently pull the plant from its pot; after one year you should have new, white healthy roots filling the pot. If the roots are dark or there are few roots left from overwatering that is a problem.  

The soil should not be soggy or smelly.

Quality of potting mix can also have an effect on plant drainage.

On the other hand; very excessive heat will cause leaves to fold and very excessive heat can cause stress and yellowing.  But that would need to be quite excessive.  Probably hotter than you would comfortably live with.