Please Help Me!

[chann100590]

ok so i got my first tank about 6 months ago now, its an interpet 64 which means its 64 ltrs which is equivelant to 18 gallons.
at first i had 3 silvertip tetras in there and 3 minnows, all my minnows and 1 silvertip died straight away cus i didnt cycle my tank properly 8-( so 2 of my silvertips were left, so i thought i would add some new fish 2 months ago, but obvisley i had to check the ph level and amonia everything was fine except my ph which was at 8.4, so i got a ph lowering kit and now its 7.8 that took me about a month to do, after everything was fine i bought 2 male guppies about 1 month ago and they were fine, 2 weeks after that i bought 3 female guppies, 2 days after 1 of my female guppies had died, i was thinking it was due to the stress, then 1 week after 1 of my silvertip died....

so now i have 1 silvertip and 2 male guppies and 2 females. the problem is my males look very sick, they are just sitting on the gravel at the bottom and they wont eat, 1 of my males has like a single white spot on him, they were fine earlier.. and i looked to see if there was anything wrong with my females, and one of them look like her eye has like a white patch over it, ... i really dont know what i am doing wrong, i do a water change every week (25%) and i feed them once a day.

please someone help me

 

[stang1]

What are your water readings for ammonia, nitrite and nitrate?
The fish sitting on the bottom usually means that there could be a problem with water quality.