Even with a good start, middle-of-the-fleet sailors have to deal with boats in front of them. It's really important to stay in clean air, especially on the first windward leg when the boats are more bunched up. There are two ways to do this. The first is visual.
If you're green and red is between you and where the wind is coming from, then you might think that you're sailing in bad air. This would be true if you're not moving (in which case you have other problems!) But when you're moving, the apparent wind shifts forward so you're probably OK for now.
You'll get the best reading if red has a wind indicator at the top of its mast.
You'll be surprised by how long you can hold this position. This is especially important when sailing in a group, and being able to do this is called "holding your lane."
It's like a get-out-of-jail-free card because holding your lane as long as possible helps you stay with the leaders as the rest of the fleet thins out behind you.
As mentioned, there's a second way to tell when you're sailing in bad air and that's by feeling. You'll feel your boat hesitate and slow down. You can also feel a slight turbulence on your face. When this happens, it's time to look at your options: bear off to get a little speed and clear air or tack if you can. If you want to stay with the group, putting in 2 tacks to get clean air is better than sailing in bad air.