Is pH important? Yes. Buffering capacity of water matters more than the specific tested pH level itself. Meaning that the ability of water to maintain pH is important hence hardness levels come into play. Having a pH of 7.6 that is stable is far better than having an initial 7.8 with little buffering capacity. Where many come unstuck is by testing the tap water for pH only at water change - if that water then has next to no buffering capacity the pH can rapidly fall. How important depends on species but pH shock can and does kill fish. Do shops and wholesalers monitor pH? Many do yes. Do they adjust settings for every tank? No. Generally (meaning there are exceptions - Discus, Tangs etc) they will maintain their tanks at an 'average' parameter setting. Ask your supplier / shop what pH they maintain. Some sources of tap water may be satisfactory straight from the tap (excluding chlorine neutraliser) - others aren't.
The above advice is intended for Malawi Cichlids and the like.
If this is in reference to your Frontosa then I would advise investigating your hardness levels. I would also enquire as to the parameters of your fish supplier. 7.5 with little buffering capacity would need to be addressed. 7.5 is low for Tanganyikans. Many Frontosa breeders maintain 8.0+. 8.0 to 7.5 is a very big difference. Old school plastic corner filter loaded with shellgrit is one easy way to help buffer. If Frontosa were wild caught or recent gen you'd really want to be doing everything to replicate wild conditions.
Ph doesn't really matter as much as stability. Constantly trying to change your ph through chemicals can result in swings, so natural, long term methods are far better.
Unless we are talking wildcaught fish, or very extreme Ph values, I think our domestically bred fish do much better without fluctuation.