Do you think there is any concern over soil pH or other soil measurements?
When practicing landscape design years ago I always got a thorough soil analysis done and especially with new construction. Top soil came and went depending on how sites were graded to the point you could not tell what was going on between the front, back and side yards. University of California extension used to do residential soil testing for free from samples prepared to their specs. Long gone are those days but soil testing is not expensive and can save lots in money wasted on fertilizers and so forth soil is incapable of metabolizing.
You can and should home test kit for Ph every season or so if nothing else. I think the home kits with the strips are $20. Don't go crazy buying lots of strips as the chemical reagents will break down before you get to use them.
The more you describe how you came to find your plants, I suspect you may have created a watering problem but would also suggest the nursery stock was not well taken care of to start. In California nursery stock was sold in containers so you had a fighting chance of keeping it alive until it was sold and planted. Here we do the ball and burlap or plastic wrap alternative. And you don't know how long that hibiscus was on the truck before just laid out on the concrete before whatever period of time before you bought it.
Not to harp on box stores again but there is something to be said about getting plants from a real nursery. I do know all the box stores advertise their plants will grow or your money back? If I were you, I would be thinking about asking for your money back if my water tool does not help or pulling the plant out and replanting at with roots trimmed does not either.
Do you have receipts. I have no idea what you need to return plants that fail to box stores but I think you should think about doing so with your hibiscus and rasberries soon if the soil thing I mentioned and further breaking apart the root ball does not help.