Hello,
with thanks to Birdboybowley and all that corrected me in another recent Tern thread:
First bird: with only a small black spot on the-coverts and a tiny isolated dark cap on the rear crown, this surely has to be a White winged Tern.
Second picture: lower bird is the bird from the first picture?
The upper bird is difficult for me. Restricted head pattern is just within variation for a Black Tern, but yes, better for a White winged Tern (with so much white above the eye). Do you have more pictures? This bird seems to have a dark shoulder mark, position and feeling seems real to me. If this is not an artefact, than its a Black Tern imo. (Thing that disturbs me is that the mark seems blurred with a distinct point at the end, an unusual pattern for a Black Tern?)
Third bird: do you have more pictures? Because the wing covers the head-pattern and blur and artefacts seems to obscur or even alter the shape and extent of the bill in an appearantly bad way (no offense you know). (if forced, I would opt for a White-winged Tern, but prepared to be corrected by others and new pictures)
I hope for more pictures and comments!