What's your question? Ask

It is much too difficult to provide and maintain exact pH of each around each area, and the results are negligible. There are chemical reasons why blues require an acidic environment, but this is a very complicated subject. The exact values will be within a few tenths of a point of each other, so it is not really feasible to try and keep this constant. In reality, as long as the pH is between 6 and 6.9 they will be just fine.

They can be a little picky about their watering. Usually, overwatering causes this more than underwatering. Sometimes this can be do to lack of nutrients, but the way its forming doesn't fit the bill.

Make sure that these have plenty of time for the soil to dry out between waterings. I would also apply a half cup of DOLOMITIC LIME and a teaspoon of WETTABLE SULFUR to mitigate any infection trying to set in. Do this once per year for more protection.

This article will help you to care for Hibiscus: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-container-care.htm

Hibiscus is one of the plants that Japanese beetles prefer. These are shiny, part green beetles that are active for several weeks at this time of year. You can catch them with a hand-held vacuum and dump the contents into a pail of soapy water. Or you can go into the garden twice daily and sweep the beetles into a soapy water pail. If the infestation is really bad, get out there 3 times a day until they are under better control. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/insects/japanese-beetles.htm
If these beetles are an annual problem, think about treating the lawn for grubs at the appropriate time in spring. Grubs are the larvae of beetles. https://www.gardeningknowhow.com/plant-problems/pests/insects/get-rid-of-grub-worms.htm
If you don't think Japanese beetles are your problem, please catch a picture of the insect and create a new post here.

This could be due to a pest issue.
This article will help you.

https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-flowers-hibiscus-blossoms-falling-off-plant.htm

In your area, this thing will struggle to survive winter, even with covering. I would recommend burlap, heavy mulching, anything that it a HEAVY insulator. These are hardy to zone 5, and you are in zone 4.

With this being said, It may not get huge. More than likely it will die back to the ground anyway, coming up from brand new fresh growth each year... With heavy protection in the winter that is.

However, with very heavy protection, and leaving some of the stump, you may successfully keep some old growth alive. This will allow for a larger shrub

This is from a long infestation of White Flies.

This article will help you.

https://www.gardeningknowhow.com/plant-problems/pests/insects/whitefly-control.htm