Workout advice

Hi knowledgeable people!
I've been going to the gym for a month now although I had an enforced 2 week break due to my little monster giving me chickenpox.
I have 49lbs further to lose until i'm at the middle of my healthy BMI range. 28lbs until the top of that range.

During the week I have an hour spare and weekend I can get away for 90 mins.
I have 2 workouts which I alternate Tues, Thurs, Sat and Sun

I do a mix of cardio and weight machines. No free weights currently.

Workout Tues & Sat
Rowing machine 20 - 30 mins
Elliptical 15 - 20 mins
Pec Fly 3x10
Chest Press 3x10
Shoulder Press 3x10
Leg Press 3x10

Workout Thurs & Sun
Rowing machine 20 - 30 mins
Elliptical 15 - 20 mins
Lat pulldown 3x10
Back Extension 3x10
Leg Extension 3x10
Ab crunch 3x10
Bicep curl 3x10

The cardio I am definitely seeing an improvement. I started at 5 and 10 min intervals on the machines and now can do 20 at higher intensity on both the rower and elliptical.

The weights I can have days when I breeze through and other days i'll struggle on the same weights. This means i'm unsure about when or if I should be increasing weight. I especially struggle with the shoulder press although this may be a hangover from a car accident i'm having physio for.

What would you change or add in to this routine? Is this balanced enough? Should I be pushing for a higher weight every week? Should I be able to complete the 3x10 sets or should I fail on the 3rd set?

Thanks in advance