Help! My tanks water ph keeps changing.

Please help me. I dont know what to do anymore.

I have a 70 litre tank ish, 60 * 30 * 35 cm.

ive got 4 Mollies, 10 - 13 babie Mollies, 3 Neon Tetras, 4 Guppies 2
are pregnant, 1 cat fish (cant remember name) and 4 shrimp.

Im new to this, My tank has been running about since the 18th of
October this year. Ive had plants in the aquarium but took them out as
ive added (Proper PH 7.0) from Aquarium pharmaceuticals inc.

This would kill all plants apparently, they are currently in bucket.

1st of all my water went up 2 8.4 PH

Now its at bout 6.0 perminantly and i cant get it to raise up at all.
ive been doing water changes at least once a day too.

Stuff ive been adding to tank........

Nutrafin cycle. (Every few water changes)
Api tap water conditioner (Every water change)
Ph up (Every day till i ran out)
Proper PH 7.0 (Once yesterday)
Kingfisher British prof safe guard (Anti stress) tap water conditioner
(Once with water change yest) as ive run out of Api.

Please help me ive all ready lost bout 8 young mollies. they about 10
days old. i dont know what else to do. Apparently ive got quite high
ammonia but im doing water changes to try an combat that prob.