I tested 4 landers for a iPhone X campaign, one of the landers is doing >55% CTR while all others <10%.
Should I just cut off all other landers and use this one only? Or should I wait to see the actual CR of each? (this will burn me much more $$$)
Thanks!
Before you cut you should wait for some data to come in.
High CTR could be just thanks to an aggressive scripts like back button redirect.
Wait for some conversions or spend at least 3x of your payout (or less or more depending how high it is)
Yup, CR is a much more important metric compared to CTR. Have a look at vortex's thread on cutting landers. Ideally you'd collect enough data to reach statistical significance, which is a point where you can say with confidence that one lander is better.
Share screenshots if you can 
Are you testing just 1 offer?
If you used LPs from a spy tool that should be proved I think the offer here is the weak part.
Test more offers.