Part 107 pilot reported a lost link during a flight. The UAS collided with a tree and crashed.

Narrative

I was employed as one of two remote pilots by Company; to shoot video of the racers at the Event in ZZZ; along the River; Date. Each pilot was given their own controller and sUAS to operate. After my pre-flight inspection; I was directed to pilot the sUAS to a position upriver; approximately 2;200 feet from the takeoff/landing zone to film the rowers as they raced to the finish line; where the operations were based.On Date at approximately XA:30 local time; as I awaited the racers on my third or fourth run of the day; I received a weak link warning and I attempted to maneuver the drone to a position with a stronger radio contact. The maneuver failed and the drone collided with a tree and fell to earth.A second incident occurred on Date 1; at approximately XA:00 local time. I was videoing the racers from a parallel position; tracking the racers; at an altitude of 15-20 ft AGL when my drone collided with a tree and fell to earth.There was a third incident. I did not witness it; but on Date at approximately XB:00 local time; the other drone pilot told me that his drone had been lost in a tree in the woods behind the grandstand. The picture link was still active and although he could identify a cell tower on the far side of the river in the image from the drone; he could not identify in which tree the drone lay and was unable to recover it.To my mind; the use of a visual observer for each drone and/or more centrally locating the ground station in relationship to the area being covered by the sUAS's would greatly improve the margin of safety for the spectators. Additionally and ideally; a drone pilot should be included in planning meetings to adjust the personnel's awareness of issues they are perhaps not likely to be aware of.I am a student at School in their drone program. I was a last minute hire on this job and I didn't think through the implications of the job when I showed up at the event site that morning.