I have half a dozen hibiscus in my backyard, some getting lots of sun and some getting only a little. All are on the same drip system, so they get about the same amount of water each day. Those with lots of sun are doing okay; the others have a serious problem. My guess is they're getting too much water, but I can't find a happy medium for all the bushes.
Burned Edges and Yellow Leaves on Hibiscus
Certified GKH Gardening Expert
Brown edges actually normally indicate that the plant is getting too little water. There may be some issues with the drip line or it may be that they have been overwatered to the point that they have developed root rot and can't take up water due to this. This article will help you determine if root rot is the issue:
If the ones in the shade are getting too much water, is it possible that they do not need to be on the drip line? They may be able to get enough water naturally to survive in the shade without outside watering.