Issues:

At what times does rule 18 apply between the boats to confer mark room?

See Rule 18.1 and 18.2

Was yellow entitled to tack onto port tack?

See Rule 10 and Rule 13

Was yellow entitled to tack onto starboard?

See Rule 18.4

If yellow committed a foul at what point was it required to sail well clear of the other boats and do penalty turn(s)? See Rule 44.

Was yellow entitled to mark-room after it tacked onto port?

Was yellow entitled to mark-room after it tacked onto starboard?

Was there a boat entitled to mark-room at all times? If not, what Rules governed the mark rounding when Rule 18 did not apply?