Alkaline or limey soil
A normally or average soil pH is around pH 6.5, with an acid soil such as peat soil being around pH 5.5 and a chalky soil which is alkaline being around pH 7.0
Your soil came back as pH 7.8 so it’s very alkaline. ( very limey )
Each type of species of plant has evolved or adapted to access nutrients in the soil at a certain soil pH level. For example, Rhododendrons naturally grow on forest floors in shade in the leaf litter, the leaves that fall every year. This leaf litter and the resulting soil is acidic but the Rhododendrons can access the nutrients in the soil at this level of soil pH.
At the other end of the scale, daisies can access soil nutrients in alkaline soils.
The soil pH is very high alkaline, this might be natural or if its a new build often building products such as dropped cement mortar can raise the soil pH
The solution is to lower the soil pH near to soil pH 6.5 which means using acidic treatment to lower the soil pH.
These treatments can be natural such as using well-rotted horse manure or farmyard manure as a mulch or digging it into the soil.
Both well-rotted horse manure or farmyard manure have a low pH
In addition, you can use chemical treatments such as
Liquid tomato feed as a liquid feed
Growmore fertilizer one handful sprinkled over a square metre
Iron sulfate sprinkled onto the soil and watered in
These products should be available at your local garden centre