Soil Help (Ph 5-6.5)?

I bought (SUBSTRAL Terra Magma) with pH 5-6.5. Can I add any fertilizer in the blooming phase or flowering phase or when I irrigate plant or I have just to use this bought soil without any fertilizer until the end of growing? When I water plant, do I have to use water with pH in 6.3-7 range or it is better to use tap water? If necessary and if someone has experience, I would appreciate any comment when I should start with fertilization. Do I need to add perlite to this soil? I also bought and worm castings, can I add worm castings this soil or it wont be good, I am asking this because it is already prepared soil? In shop where I bought this worm castings, shop assistant told me that it can not burn the roots of the plant and that I can use it during the whole growing period.

Yo

Soil : Usually soil has fertilizers added and the bag should tell you how long you can go without adding any (usually 3 weeks here in SA until any is needed)
Water : Better to use mineral water as you know what the PH range is thats what i do if you want you can use tap water but u have to let it sit for a day or 2 because of the chlorine
Perlite: Basically lightens the soil mixture prevents soil compression and help in drainage

Thats all i know

Maybe there write something, but it is in German.
There are write: peat, wood fiber, bark, green compost, clay minerals.
Available nutrients:
100-600 mg/l N
100-500 mg/l P2O5
400-1000 mg/l K2O
pH (CaCl2): 5-6.5
salinity (KCl) in g/l FM < 3

Nothing more.

Hmmm give me a couple mins nd ill check it owt

Ok i checked it fertilizers are added for the first 6-8 weeks of growth u will be good, BTW it wasn't German it was Slovenian Peace +REP???

It is maybe Slovenian, but on the bag it is written in German.
What about adjusting the pH value of irrigation water?

dont worry about the language yes that would be a good idea i recommend mineral/bottled water as you know the PH range and it has no chlorine flouride and other things in it best use a PH between 6-7 (7 and above = becomes alkaline 6 and below = becomes acidic)