Some of your joints probably had a little too much solder and were a bit blobby. I would suggest using a good tacky flux added to assist in the solder flowing nicely (personally use Amtech NC-559-V2-TF). I also like to use knife tips on my soldering iron for doing very small components like these, the fine point of the tip helps to solder to small parts effectively.
Better to have too much than too little. 😄 Having too much doesn't have many negative effects in this case with smd resistors, it's unnecessary but won't harm the resistor, in my opinion.
You don't need a microscope. You can buy cheap magnifying glasses or even spectacles - with LED lights. Look at other 'crafts' supply - not just electronics. Even basic Helping Hands usually come with a magnifying lens.
Using tweezers to hold such small components by their sides while soldering, is very risky. If the solder has hardened and your hand shakes even a tiny bit, you risk cracking the component. A modified toothpick, to push at a 45 degree angle at the component by it's back edge , into the solder; is a much less risky way.
