Add the tempura batter to a bowl and whisk vigorously for a good minute *important* this will ensure there are no more 'flour' bumps. The batter should be a light creamy yellow.
Dip your veggies and shrimps inside the batter, coat nicely and fry in the preheated oil on both sides until cooked through and the batter is golden brown. Transfer to a grill or some kitchen paper to absorb the excess oil.*If you let the batter sit for a while, make sure to whisk it back together for 20 seconds or so to ensure perfect consistency in you tempura every time.
Whey Protein Isolate has less carbs than normal whey protein so try that use that :)
I recommend eating these the same day if you're just going to eat them as is or with some dipping sauce. However, if you coat the tempura in some sauce like sweet chili or anything like that, they'll be good in the fridge for a couple of days.